From WordNet (r) 3.0 (2006):
B n 1: aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil [syn: bacillus, B] 2: originally thought to be a single vitamin but now separated into several B vitamins [syn: B-complex vitamin, B complex, vitamin B complex, vitamin B, B vitamin, B] 3: a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder [syn: boron, B, atomic number 5] 4: a logarithmic unit of sound intensity equal to 10 decibels [syn: Bel, B] 5: (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter [syn: barn, b] 6: the 2nd letter of the Roman alphabet [syn: B, b] 7: the blood group whose red cells carry the B antigen [syn: B, type B, group B]