BoronThe chemical element commonly used as the dopant in solar photovoltaic device or cell material.
BorrowMaterial excavated from one area to be used as fill material in another area.
Borrow areasGenerally, surface areas, that contain borrow pits. The area from which material for an embankment is excavated.
Borrow materialMaterial such as soil or sand that is removed from one location and used as fill material in another location.
Borrow pitA pit or excavation area used for gathering earth materials (borrow) such as sand or gravel.
Borrow pitsSpecific site(s) within a borrow area from which material is excavated for use.
Bottled GasA generic term for liquefied and pressurized gas, ordinarily butane, propane, or a mixture of the two, contained in a cylinder for domestic use.
Bottom ashNoncombustible ash that is left after solid fuel has been burned.
Bottoming cycleA means to increase the thermal efficiency of a steam electric generating system by converting some waste heat from the condenser into electricity.
BoulderA rock fragment, usually rounded by weathering or abrasion, with an average dimension of 12 inches or more: will not pass a 12-inch screen.
Boulder clayA geological term used to designate glacial drift that has not been subjected to the sorting action of water and therefore contains particles from…
bound waterCellular water not released into the intercellular space upon freezing and thawing. Opposite: free water.
Boundary LayerIn general, a layer of air adjacent to a bounding surface. Specifically, the term most often refers to the planetary boundary layer, which is the layer…
Bounded Weak Echo Region (BWER)(Also known as a vault.) Radar signature within a thunderstorm characterized by a local minimum in radar reflectivity at low levels which extends upward…
bovine somatotrophin(Abbreviation: BST) A natural protein in cattle. It has been cloned, using recombinant DNA technology, expressed in large amounts and marketed as an…
Bow EchoA radar echo which is linear but bent outward in a bow shape. Damaging straight-line winds often occur near the "crest" or center of a bow echo.
Bowen RatioFor any moist surface, the ratio of heat energy used for sensible heating (conduction and convection) to the heat energy used for latent heating…
Box girderA hollow steel beam with a square or rectangular cross section.
Box ModelA computer model used to calculate air pollution concentrations. A box model is based on the assumption that pollutants are emitted into a box through…
Boyle's lawWhen the temperature is held constant, the pressure and density of an ideal gas are directly proportional.
Brake horsepowerThe brake horsepower of a pump is the actual motor input horsepower required to produce the hydraulic horsepower from a pump (flow and head) taking into…
BranchAn addition to the main pipe in a piping system.
Brash IceAccumulation of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice.
Brayton CycleA thermodynamic cycle using constant pressure, heat addition and rejection, representing the idealized behavior of the working fluid in a gas turbine type…
BRC- Budget Review Committee, Bureau Procurement Chief.
BRCA1/BRCA2The first breast cancer genes to be identified. Mutated forms of these genes are believed to be responsible for about half the cases of inherited breast…
Bread Box SystemThis simple passive solar hot water system consists of one or more storage tanks placed in an insulated box that has a glazed side facing the sun.
BreakersWaves that break, displaying white water. Depends on wave steepness and bottom bathymetry.
BreakupThe time when a river whose surface has been frozen from bank to bank for a significant portion of its length begins to change to an open water flow…
Breakup DateDate on which a body of water is first observed to be entirely clear of ice and remains clear thereafter.
Breakup JamIce jam that occurs as a result of the accumulation of broken ice pieces.
Breakup PeriodThe period of disintegration of an ice cover.
BrecciaA sedimentary rock formed of coarse-grained material consisting of sharp fragments embedded in clay or sand.
Breccia (volcanic breccia)Conglomerate-like rock made up of angular pieces of volcanic rock usually bound in volcanic ash.
BrecciatedA rock made up of highly angular, coarse fragments.
breed1.a sub-specific group of domestic livestock with definable and identifiable external characteristics that enable it to be separated by visual appraisal…
breed at riskAn animal breed that is in danger of becoming extinct because its population has fallen below a critical number.
breedingThe process of sexual reproduction and production of offspring.
Breeding densityDensity of sexually mature organisms in a given area during the breeding period.
Breeding potentialMaximum rate of increase in numbers of individuals of a species or population under optimum conditions.
Breeding rateActual rate of increase of new individuals in a given population; the breeding potential minus limiting factors.
breeding valueA quantitative genetics term, describing that part of the deviation of an individual phenotype from the population mean that is due to the additive…
bridgeA filter paper or other substrate used as a wick and support structure for a plant tissue in culture when a liquid medium is used.
Bridge, Class AA bridge located on a Federal-aid highway. Examination of this type of bridge is required every 2 years with an in-depth examination every 6 years.
Bridge, Class BA bridge not located on a Federal-aid highway that is used by the public. Examination of this type of bridge is required every 3 years.
Bridge, Class CA bridge not located on a Federal-aid highway that can be designated as being a private or operating bridge and could be gated or closed to the public, if…
Bright BandThe enhanced radar echo of snow as it melts to rain.
Bright Surge on the Disk (BSD)In solar-terrestrial terms, a bright gaseous stream (surge) emanating from the chromosphere.
Bright Surge on the Limb (BSL)In solar-terrestrial terms, a large gaseous stream (surge) that moves outward more than 0.15 solar radius above the limb.
BrightnessA basic visual sensation describing the amount of light that appears to emanate from an object, or more precisely, the luminance of an object
BrineWater saturated or strongly impregnated with salt.
Brisk Wind AdvisoryA Small Craft Advisory issued by the National Weather Service for ice-covered waters.
British thermal unitThe quantity of heat required to raise the temperature of one pound of water one degree of Fahrenheit at or near 39.2 degrees Fahrenheit.
British thermal unit (Btu)The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories.
British thermal units (Btu)Quantity of heat required to raise the temperature of one avoirdupois pound of water 1 degree F at or near 39.2 degrees F.
BRMbusiness reference model - an organized, hierarchical way to describe the day-to-day business operations of the Federal government; this model presents…
BRN(Bulk Richardson Number) A non-dimensional number relating vertical stability and vertical shear (generally, stability divided by shear).
Broad-crested weirAn overflow structure on which the nappe is supported for an appreciable length in the direction of flow. See weir.
broad-host-range plasmidA plasmid that can replicate in a number of different bacterial species.
broad-sense heritabilityThe proportion of the total phenotypic variation which results from genetic variation or interaction between the genotype and the environment.
BroadbandCommunications of high capacity and usually of multimedia content.
Broadband noiseNoise that has a continuous spectrum, that is, energy is present over a wide range of frequencies.
Broadcast burnControlled fire over the entire surface of a designated area.
Brocken SpecterAn optical phenomenon sometimes occurring at high altitudes when the image of an observer placed between the sun and a cloud is projected on the cloud as…
Broken LevelA layer of the atmosphere with 5/8 to 7/8 sky cover (cloud cover).
BrokerAn agent who handles the public's orders to buy and sell securities, commodities or other property. A commission is generally charged for this service.
broodstockThe group of males and females from which fish are bred.
BrownfieldsSites that are underutilized or not in active use, on land that is either contaminated or perceived as contaminated.
browningDiscolouration of freshly cut surfaces of plant tissue due to phenolic oxidation.
BrownoutThe partial reduction of electrical voltages. A brownout results in lights dimming and motor-driven devices slowing down. See blackout.
BrowseTwigs, leaves, and young shoots of trees and shrubs that animals eat.
BryophytesPlants of the phylum Bryophyta, including mosses, liverworts and hornworts, characterized by the lack of true roots, stems and leaves.
BryozoanAquatic colonial animals with branching, mossy or fan-like growth. They resemble corals but have more complex nervous, muscular, and digestive systems.