Source : Webster's Revised Unabridged Dictionary (1913)

Coma \Co"ma\, n. [L., hair, fr. Gr. ko`mh.]
   1. (Astron.) The envelope of a comet; a nebulous covering,
      which surrounds the nucleus or body of a comet.

   2. (Bot.) A tuft or bunch, -- as the assemblage of branches
      forming the head of a tree; or a cluster of bracts when
      empty and terminating the inflorescence of a plant; or a
      tuft of long hairs on certain seeds.

   {Coma Berenices}[L.] (Astron.), a small constellation north
      of Virgo; -- called also {Berenice's Hair}.

Source : WordNet®

Coma Berenices
     n : a constellation in the northern hemisphere between Ursa
         Major and Bootes; contains a cluster of some 10,000
         galaxies