Base Layer: The layer of clothing that is worn next to the skin. Normally associated as a wicking garment. Sweat is drawn away from the surface of your skin to the outer surface of the fabric. If sweat is left on the skin the process of evaporation cools the body rapidly.
Baseplate: the see-through plate of an orienting compass onto which the compass housing is mounted.
Bathtub Floor - Tents: Bathtub floors are floors that curve upward at their perimeter in a way that often join to the canopy of the tent. Bathtub floors eliminate the floor perimeter seam and therefore keep tents inner stitching away from ground moisture, adding to a tent's waterproof-ness. They can often reduce the weight and increase the strength of the tent with wings that help to pull the walls taut. bathtub floors are becoming fairly common in family, ultralight and expedition tents.
Bivy: Unplanned or temporary location for a camp or overnight stay.
Boxwall - Sleeping Bags: The sleeping bags baffle sidewalls which keep the insulation in place are vertical, hence the baffle shape is box-like. Several types of boxwall designs exist, including rectangular, diamond shape and curved. They all have one thing in common, however, which is the vertical baffle sidewalls.
Breathable: A term that denotes the rate of water vapour transmission through a fabric. This movement of water vapour is driven by the difference in concentration of water vapour (or humidity) between the surface of the skin and the air outside the garment, as well as the physical resistance of the fabric layers. Usually quoted as gms of water vapour per metre squared of fabric.