BLAbbreviation for Boundary Layer; a layer of air adjacent to a bounding surface.
Black BodyA hypothetical object that absorbs all of the radiation that strikes it; also emits radiation at a maximum rate for its given temperature.
Black Body SpectrumA plot of the intensity of radiation versus wavelength for a black body.
Black CarbonOperationally defined species based on measurement of light absorption and chemical reactivity and/or thermal stability; consists of soot, charcoal…
black carbon concentrationThe concentration of carbon in its very absorbing, elemental, non-organic, non-oxide form (e.g. graphite).
Black IceTransparent ice formed in rivers and lakes, or on roads and bridges.
Black waterLiquid and solid human body waste and the carriage water generated through toilet usage.
BlackbodyAn ideal substance that absorbs all radiation falling on it, and reflecting nothing.
Blackbody RadiationThe electromagnetic radiation emitted by an ideal blackbody adhering to the radiation laws; it is the theoretical maximum amount of electromagnetic…
BlackoutThe disconnection of the source of electricity from all the electrical loads in a certain geographical area brought about by an emergency forced outage or…
bladeUsually a part of an excavator which digs and pushes dirt but does not carry it.
blast cellA large, rapidly dividing cell that develops from a B cell in response to an antigenic stimulus.
Blasting matsA blanket usually composed of woven cable or interlocked rings placed over a blast to reduce flyrock.
BlastocoelThe fluid-filled cavity inside the blastocyst of the developing embryo.
BlastocystA mammalian embryo (fertilized ovum) in the early stages of development, approximately up to the time of implantation.
Blastocyst stageAn early stage in the development of embryos, when (in mammals) the embryo is a spherical body comprising an inner cell mass that will become the fetus…
blastomereAny one of the cells formed from the first few cleavages in animal embryology. The embryo usually divides into two, then four, then eight blastomeres, and…
BlastulaIn animals, an early embryo form that follows the morula stage; typically, a single-layered sheet (blastoderm) or ball of cells (blastocyst ).
bleeding1. Collection of blood from immunized animals. 2. Used to describe the occasional purplish-black colouration of media due to phenolic products given off…
Blender PumpA fuel dispenser that draws fuel from two separate storage tanks and can dispense preprogrammed blends of those two fuels.
BlightPhysical and economic conditions within an area that cause a reduction of or lack of proper utilization of that area.
Blizzard(abbrev. BLZD)- A blizzard means that the following conditions are expected to prevail for a period of 3 hours or longer: Sustained wind or frequent gusts…
Blizzard WarningIssued for winter storms with sustained or frequent winds of 35 mph or higher with considerable falling and/or blowing snow that frequently reduces…
blockA repetition/replication of the Early, Mid and Late Seral Treatment plots and a Control plot. See Repetition/replication.
Block Group (BG)A cluster of census blocks having the same first digit of their four-digit identifying numbers within a census tract.
Block-faulted (mountains)Landforms formed by the movement (uplift and tilting) of large crustal blocks during an extensional episode.
Blocked FlowFlow approaching a mountain barrier that is too weak or too stable to be carried over the barrier.
BlockloadingProviding a consistent amount of electrical power in a stated period of time.
Blood Cell SeparatorA machine, used in apheresis, which distinguishes the small fraction of stem cells in the blood from all other blood cells, so that the stem cells may be…
blotAs a verb, to transfer DNA, RNA or protein to an immobilizing matrix. As a noun, the immobilizing matrix carrying DNA, RNA or protein.
BlowdownPeriodic removal of water from an evaporative cooling system (also known as a wet closed-cycle cooling system) to control the buildup of impurities and…
BlowerThe device in an air conditioner that distributes the filtered air from the return duct over the cooling coil/heat exchanger.
Blower DoorA device used by energy auditors to pressurize a building to locate places of air leakage and energy loss.
BlowingA descriptor used to amplify observed weather phenomena whenever the phenomena are raised to a height of 6 feet or more above the ground
Blowing Dust or SandStrong winds over dry ground, that has little or no vegetation, can lift particles of dust or sand into the air.
Blowing SnowBlowing snow is wind-driven snow that reduces surface visibility. Blowing snow can be falling snow or snow that has already accumulated but is picked up…
Blown In Insulation (see also Loose Fill)An insulation product composed of loose fibers or fiber pellets that are blown into building cavities or attics using special pneumatic equipment.
BlowoutA wind-eroded section of a sand dune caused by a disturbance or removal of the vegetation.
Blue topsGrade stakes whose tops indicate finish grade level.
BLZDBlizzard- A blizzard means that the following conditions are expected to prevail for a period of 3 hours or longer: Sustained wind or frequent gusts to 35…
BMPA Windows file format for storing bit map images.
BOD5The amount of dissolved oxygen consumed in five days by biological processes breaking down organic matter. See biochemical oxygen demand.
BoilerA vessel or tank where heat produced from the combustion of fuels such as natural gas, fuel oil, or coal is used to generate hot water or steam for…
Boiler FeedwaterThe water that is forced into a boiler to take the place of that which is evaporated in the generation of steam.
Boiler HorsepowerA unit of rate of water evaporation equal to the evaporation per hour of 34.5 pounds of water at a temperature of 212 degrees Fahrenheit into steam at 212…
Boiler PressureThe pressure of the steam or water in a boiler as measured; usually expressed in pounds per square inch gauge (psig).
Boiler RatingThe heating capacity of a steam boiler; expressed in Btu per hour (Btu/h), or horsepower, or pounds of steam per hour.
BolideInformally defined as an exploding meteor that resembles a bright fireball.
Bolson (floor)A term applied to an internally drained (closed) intermontane basin in arid regions where drainages from adjacent mountains converge toward a central…
BombPopular expression of a rapid intensification of a cyclone (low pressure) with surface pressure expected to fall by at least 24 millibars in 24 hour.
BONThe necrosis (death) of bone tissue caused by treatment with a bisphosphonate (a drug or substance used to treat osteoporosis, bone pain caused by some…
Bone (Oven) DryIn reference to solid biomass fuels, such as wood, having zero moisture content.
Bone dryHaving zero percent moisture content. Wood heated in an oven at a constant temperature of 212 degrees F or above until its weight stabilizes is considered…
Bone dry ton(or "oven dry ton"). An amount of wood that weighs 2,000 pounds at zero percent moisture content.
Bone Dry UnitA quantity of (solid) biomass fuel equal to 2,400 pounds bone dry.
Bone dry unit (BDU)A quantity of wood residue which weighs 2,400 pounds at zero percent moisture content.
Bone marrow(bone MAYR-oh) The soft, sponge-like tissue in the center of most bones. It produces white blood cells, red blood cells, and platelets.
Bone Marrow Aspiration(bone MAYR-oh as-pih-RAY-shun) The removal of a small sample of bone marrow (usually from the hip) through a needle for examination under a microscope.
Bone Marrow Biopsy(bone MAYR-oh BY-op-see) The removal of a sample of tissue from the bone marrow with a needle for examination under a microscope.
Bone marrow stem cell (BMSC)One of at least two types of multipotient stem cells: hematopoietic stem cell and mesenchymal stem cell.
Bone marrow stromal cellAlso known as mesenchymal stem cells, bone marrow stromal cells are a mixed population of cells derived from the non-blood forming fraction of bone marrow.
Bone marrow stromal cellsA mixed population of stem cells found in bone marrow that does not give rise to blood cells but instead generates bone, cartilage, fat, and fibrous…
bone marrow transplantation(bone MAYR-oh tranz-plan-TAY-shun) A procedure to replace bone marrow that has been destroyed by treatment with high doses of anticancer drugs or…
Bone marrow transplantation (BMTx)Trans-planta-tion of bone marrow from one individual to another. Autologous BMTx is a process in which a patient's healthy bone marrow is withdrawn and…
Bone morphogenetic proteins (BMPs)Proteins thatare involved in the formation of embryonic bone. BMPs operate at several stages in this formation of bone, beginning with the early stages of…
BonnetThe upper portion or the cover of a gate valve body.
Bonneville Power Administration (BPA)One of five federal power marketing administrations that sell low cost electric power produced by federal hydro electric dams to agricultural and…
BoraA regional downslope wind whose source is so cold that it is experienced as a cold wind, despite compression warming as it descends the lee slope of a…
Border IceAn ice sheet in the form of a long border attached to the bank or shore.; shore ice.
Borderline soilsSoils that have the characteristics of two of the classification groups in the Unified Soil Classification System.
BorealLiving in and adapted for living in the extreme northern areas of the world. This area is located just below tundra conditions.
BoreholeAny exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to…