Freak WaveA wave of much greater height and steepness than other waves in the prevailing sea or swell system. See Rogue Wave.
Free AtmosphereThe part of the atmosphere that lies above the frictional influence of the earth's surface.
Free Ground WaterUnconfined ground water whose upper boundary is a free water table.
free waterThe cellular water released into the intercellular spaces when tissue is frozen and thawed. Opposite: bound water.
free-living conditionsNatural or greenhouse conditions experienced by plantlets upon transfer from in vitro conditions to soil.
FreeboardPortion of the dam above spillway level to protect the dam against washout.
FreezeA freeze is when the surface air temperature is expected to be 32°F or below over a widespread area for a climatologically significant period of time.
Freeze WarningIssued during the growing season when surface temperatures are expected to drop below freezing over a large area for an extended period of time…
freeze-dryThe removal of water as vapour from frozen material under vacuum. Used to measure water content and to preserve samples, particularly spores.
Freeze-thaw damageDamage to concrete caused by extreme temperature variations as noted by random pattern cracking.
FreezeoutDeeply frozen over for long periods of time.
Freezeup dateDate on which the water body was first observed to be completely frozen over.
Freezing DrizzleA drizzle that falls as a liquid but freezes into glaze or rime upon contact with the cold ground or surface structures.
Freezing Drizzle AdvisoryIssued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected.
Freezing FogA suspension of numerous minute ice crystals in the air, or water droplets at temperatures below 0º Celsius, based at the Earth's surface, which…
Freezing LevelThe altitude at which the air temperature first drops below freezing.
Freezing RainRain that falls as a liquid but freezes into glaze upon contact with the ground.
Freezing Rain AdvisoryIssued when freezing rain or freezing drizzle is forecast but a significant accumulation is not expected.
Freezing SprayAn accumulation of freezing water droplets on a vessel caused by some appropriate combination of cold water, wind, cold air temperature, and vessel…
Freezing Spray AdvisoryAn advisory that may be issued within the Offshore Waters Forecast, the Coastal Waters Forecast, the Nearshore Marine Forecast, and the Open Lake Forecast…
Freezup jamIce jam formed as frazil ice accumulates and thickens.
French DrainA covered ditch containing a layer of fitted or loose stone or other pervious material.
FreonA registered trademark for a cholorfluorocarbon (CFC) gas that is highly stable and that has been historically used as a refrigerant.
FrequencyThe number of cycles through which an alternating current passes per second; in the U.S.
Frequency CurveA curve that expresses the relation between the frequency distribution plot, with the magnitude of the variables as abscissas and the number of…
Frequency demand schedulingMethod of irrigation scheduling similar to demand scheduling, but typically involves a fixed duration of the delivery, such as 24 hours.
fresh weightThe weight, including the water content, of a specimen. Synonym: wet weight.
Freshetthe annual spring rise of streams in cold climates as a result of snow melt; freshet also refers to a flood caused by rain or melting snow.
freshwaterA term referring to bodies of water that do not have salt.
Fresnel LensAn optical device for concentrating light that is made of concentric rings that are faced at different angles so that light falling on any ring is focused…
FriableA term commonly used to describe a crumb-like callus. In this state, the callus is easily dissected and readily dispersed into single cells or clumps of…
FrictionResistance to motion when one body is sliding or tending to slide over another.
Friction HeadThe energy lost from the movement of a fluid in a conduit (pipe) due to the disturbances created by the contact of the moving fluid with the surfaces of…
Friction LayerSame as Planetary Boundary Layer; the layer within the atmosphere between the earth's surface and 1 km above the surface; this is the layer where friction…
friction velocityA measure of the surface stress reflecting the effects of surface roughness and wind velocity.
Front end loaderA tractor loader that both digs and dumps in front.
FrontageThe continuous linear distance along any approved way, measured on the street line, between the side lot lines.
Frontal InversionA temperature inversion that develops aloft when warm air overruns the cold air behind a front.
Frontogenesis1. The initial formation of a front or frontal zone. 2. In general, an increase in the horizontal gradient of an airmass property, principally density…
Frost(Abbrev. FRST) - Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans.
Frost actionFreezing and thawing of moisture in materials and the resultant effects on these materials and on structures of which they are a part of with which they…
Frost AdvisoryIssued during the growing season when widespread frost formation is expected over an extensive area.
Frost heaveThe raising of a surface due to the accumulation of ice in the underlying soil or rock.
Frost lineThe greatest depth to which ground may be expected to freeze.
FrostbiteHuman tissue damage caused by exposure to intense cold.
Froude numberThe ratio of inertial forces to gravitational forces in flow. It is also the ratio of the flow velocity to the velocity of a small gravity wave in the…
Frozen DewWhen liquid dew changes into tiny beads of ice. This occurs when dew forms and temperatures later drop below freezing.
FRSTFrost- Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans.
FryImmature fish from the time they hatch to the time they become fingerlings.
Fuel cellA holding tank for a race car's supply of gasoline. Consists of a metal box that contains a flexible, tear-resistant bladder and foam baffling.
Fuel CellsElectro-chemical devices (similar to batteries) that use a continuous supply of hydrogen to produce electricity.
Fuel cycleThe series of steps required to produce electricity. The fuel cycle includes mining or otherwise acquiring the raw fuel source, processing and cleaning…
Fuel EfficiencyThe ratio of heat produced by a fuel for doing work to the available heat in the fuel.
Fuel handling systemA system for unloading wood fuel from vans or trucks, transporting the fuel to a storage pile or bin, and conveying the fuel from storage to the boiler or…
Fuel OilAny liquid petroleum product burned for the generation of heat in a furnace or firebox, or for the generation of power in an engine.
Fuel RateThe amount of fuel necessary to generate one kilowatt-hour of electricity.
Fuel replacement energyElectric energy generated at a hydroelectric plant as a substitute for energy which would have been generated by a thermal electric plant.
Fuel-adjustment clauseA provision of a power sales agreement or rate schedule that allows for the electricity price to be changed based on changes in the price of the fuel used…
Fuel-cell furnaceA variation of the Dutch oven design, that usually incorporates a primary and secondary combustion chamber (cell).
Fugitive DustThe dust released from any source other than a definable point source such as stack, chimney, or vent.
Fugitive emissionsUnintended gas leaks from the processing, transmission, and/or transportation of fossil fuels, CFCs from refrigeration leaks, SF6 from electrical power…
Fujita ScaleThe official classification system for tornado damage. The scale ranges from F0 (gale tornado, minor damage, winds up to 72 mph) to F5 (devastating…
Fujiwhara EffectA binary interaction where tropical cyclones within a certain distance (300-750 nm depending on the sizes of the cyclones) of each other begin to rotate…
Full irrigation service landIrrigable land now receiving, or to receive, its sole and generally adequate water supply through facilities which have been or are to be constructed by…
Full poolVolume of water in a reservoir at normal water surface. The reservoir level that would be attained when the reservoir is fully utilized for all project…
Full SunThe amount of power density in sunlight received at the earth's surface at noon on a clear day (about 1,000 Watts/square meter).
Full-Physics Numerical ModelA computer model used to calculate air pollution concentrations. A full-physics numerical model uses a full set of equations describing the thermodynamic…
Full-time equivalent (FTE)Equivalent to a full-time worker/employee. For example, two people, each working half time, constitute one FTE.
FumigationA pattern of plume dispersion produced when a convective boundary layer grows upward into a plume trapped in a stable layer.
functional foodA foodstuff that provides a health benefit beyond basic nutrition, demonstrating specific health or medical benefits, including the prevention and…
Functional genomicsThe field of research, that aims to determine patterns of gene expression and interaction in the genome, based on the knowledge of extensive or complete…
Fundamental InteractionsIn the Standard Model the fundamental interactions are the strong, electromagnetic, weak, and gravitational interactions (forces).
Fundamental ParticlesA particle with no internal substructure. In the Standard Model the quarks, leptons, photons, gluons, W+ and W- bosons, and the Z bosons are fundamental.
FungiPlant-like organisms with cells with distinct nuclei surrounded by nuclear membranes, incapable of photosynthesis.
FungicideAn agent, such as a chemical, that kills fungi.
fungusA plant-like organism that does not make chlorophyll. Mushrooms, yeasts, and molds are examples. The plural is fungi.