Source : Webster's Revised Unabridged Dictionary (1913)

Ab \Ab\ ([a^]b), n. [Of Syriac origin.]
   The fifth month of the Jewish year according to the
   ecclesiastical reckoning, the eleventh by the civil
   computation, coinciding nearly with August. --W. Smith.

Source : WordNet®

AB
     n 1: the blood group whose red cells carry both the A and B
          antigens [syn: {type AB}, {group AB}]
     2: a bachelor's degree in arts and sciences [syn: {Bachelor of
        Arts}, {BA}, {Artium Baccalaurens}]
     3: the eleventh month of the civil year; the fifth month of the
        ecclesiastical year in the Jewish calendar (in July and
        August) [syn: {Av}]
     4: the muscles of the abdomen [syn: {abdominal}, {abdominal
        muscle}]

Source : Free On-Line Dictionary of Computing

A&B
     
         A {bit signaling procedure} used in most {T1}
        transmission facilities where one bit from every sixth frame
        of each of 24 T1 {subchannels} is used for carrying
        {supervisory signaling}.
     
        [What does it stand for?  Is this the same as "{bit
        robbing}"?]
     
        (1997-05-05)