(sports) An extreme sport consisting of jumping from a fixed structure on land, using a parachute.

plural of base unit

A unit of measurement which is not itself defined in terms of other units, and from which other units may be derived. / The main unit of a computer or hi-fi system.

(not comparable, US) Situated or happening outside the boundaries of a military base.

(baseball, softball) A play where a runner on any base runs to the next base, usually while the pitcher pitches to a batter. Such a runner is liable to be put out if tagged with the ball while not in contact with any base.

plural of base metal

(idiomatic, business) The number of units of a system or product that are currently in use.

(chemistry) Any metal at the lower end of the electrochemical series that oxidizes readily. / (metallurgy) The metal to be welded (rather than that used to weld). / A common or inexpensive metal.

plural of base pair

(biology) In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds.