ab

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

• noun An abdominal muscle.

from The Century Dictionary.

• noun The eleventh month of the Jewish civil year, and the fifth of the ecclesiastical year, answering to a part of July and a part of August. In the Syriac calendar Ab is the last summer month.
• noun A prefix of Latin origin, denoting disjunction, separation, or departure, off, from, away, etc., as in abduct, abjure, etc.

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

• noun The fifth month of the Jewish year according to the ecclesiastical reckoning, the eleventh by the civil computation, coinciding nearly with August.

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

• noun slang An abscess caused by injecting an illegal drug, usually heroin.
• noun US The early stages of; the beginning process; the start.
• abbreviation abort or abortion
• abbreviation about

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

• noun a bachelor's degree in arts and sciences
• noun the muscles of the abdomen
• noun the blood group whose red cells carry both the A and B antigens
• noun the eleventh month of the civil year; the fifth month of the ecclesiastical year in the Jewish calendar (in July and August)