The Collaborative International Dictionary of English v.0.48:

Comma \Com"ma\, n. [L. comma part of a sentence, comma, Gr. ?
   clause, fr. ? to cut off. Cf. Capon.]
   1. A character or point [,] marking the smallest divisions of
      a sentence, written or printed.
      [1913 Webster]

   2. (Mus.) A small interval (the difference between a major
      and minor half step), seldom used except by tuners.
      [1913 Webster]

   Comma bacillus (Physiol.), a variety of bacillus shaped
      like a comma, found in the intestines of patients
      suffering from cholera. It is considered by some as having
      a special relation to the disease; -- called also cholera
      bacillus.

   Comma butterfly (Zool.), an American butterfly (Grapta
      comma), having a white comma-shaped marking on the under
      side of the wings.
      [1913 Webster]

WordNet (r) 3.0 (2006):

comma bacillus
    n 1: comma-shaped bacteria that cause Asiatic cholera [syn:
         comma bacillus, Vibrio comma]