The Collaborative International Dictionary of English v.0.48:

Coccus \Coc"cus\, n.; pl. Cocci. [NL., fr. Gr. ? grain, seed.
   See Cochineal.]
   1. (Bot.) One of the separable carpels of a dry fruit.
      [1913 Webster]

   2. (Zool.) A genus of hemipterous insects, including scale
      insects, and the cochineal insect (Coccus cacti).
      [1913 Webster]

   3. (Biol.) A form of bacteria, shaped like a globule.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cocci
    n 1: any spherical or nearly spherical bacteria [syn: coccus,
         cocci]