b

from The American Heritage® Dictionary of the English Language, 5th Edition.

• abbreviation Physics barn
• abbreviation bel
• abbreviation bottom quark
• abbreviation breadth
• noun The second letter of the modern English alphabet.
• noun Any of the speech sounds represented by the letter b.
• noun The second in a series.
• noun Something shaped like the letter B.
• noun The second best or second highest in quality or rank.
• noun The seventh tone in the scale of C major or the second tone in the relative minor scale.
• noun A key or scale in which B is the tonic.
• noun A written or printed note representing this tone.
• noun A string, key, or pipe tuned to the pitch of this tone.
• noun One of the four major blood groups in the ABO system. Individuals with this blood group have the B antigen on the surface of their red blood cells, and the anti-A antibody in their blood serum.

from The Century Dictionary.

• The second letter in order in the English alphabet, as it was in the Phenician, and has been in most other alphabets derived from the Phenician. (See A.)
• As a numeral, B was used by the Hebrews and Greeks, as now by the Arabians, for 2.
• As a symbol: In music, the seventh tone, or “leading tone,” of the model diatonic scale, or scale of C.
• In chem., the symbol of boron.
• In ornithology, the accessory femorocaudal muscle, one of the chief classificatory muscles of the leg.
• In mathematics, see A, 2 .
• In abstract reasoning, suppositions, etc., the second or other person or thing mentioned: as, if A strike B.
• In general, the second in any series: as, Company B (of a regiment), schedule B, etc.; in the form b, or b, the second column of a page, in a book printed in columns.
• As an abbreviation, B. stands for— Bachelor (or Middle Latin Baccalaureus), in B. A. or A. B., B. C. E., B. D., B. L., B. M., etc. See these abbreviations. In dates, before, as in B. C. or B. C., and born, as in b. 1813. In a ship's log-book, in the form b., blue sky. In hydrometric measurements, Baumé: as, 8° B. See Baumé's hydrometer, under hydrometer. Also Bé.
• or

from the GNU version of the Collaborative International Dictionary of English.

• is the second letter of the English alphabet. (See Guide to Pronunciation, §§ 196, 220.) It is etymologically related to p, v, f, w, and m, letters representing sounds having a close organic affinity to its own sound; as in Eng. bursar and purser; Eng. bear and Lat. ferre; Eng. silver and Ger. silber; Lat. cubitum and It. gomito; Eng. seven, Anglo-Saxon seofon, Ger. sieben, Lat. septem, Gr."epta`, Sanskrit saptan. The form of letter B is Roman, from the Greek B (Beta), of Semitic origin. The small b was formed by gradual change from the capital B.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The second letter of the basic modern Latin alphabet.
• noun voiced bilabial plosive
• noun The second letter of the English alphabet, called bee and written in the Latin script.
• noun The ordinal number second, derived from this letter of the English alphabet, called bee and written in the Latin script.
• abbreviation Alternative form of b..
• noun astronomy latitude in the galactic coordinate system
• noun physics barn
• noun computing bit
• noun cricket bye

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil
• noun the blood group whose red cells carry the B antigen
• noun originally thought to be a single vitamin but now separated into several B vitamins
• noun the 2nd letter of the Roman alphabet
• noun a logarithmic unit of sound intensity equal to 10 decibels
• noun a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder
• noun (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter