The Collaborative International Dictionary of English v.0.48:

Cosmos \Cos"mos\ (k[o^]z"m[o^]s), n. [NL., fr. Gr. ko`smos
   order, harmony, the world (from its perfect order and
   arrangement); akin to Skr. [,c]ad to distinguish one's self.]
   [1913 Webster]
   1. The universe or universality of created things; -- so
      called from the order and harmony displayed in it.
      [1913 Webster]

   2. The theory or description of the universe, as a system
      displaying order and harmony. --Humboldt.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cosmos \Cos"mos\, n. (Bot.)
   A genus of composite plants closely related to Bidens,
   usually with very showy flowers, some with yellow, others
   with red, scarlet, purple, white, or lilac rays. They are
   natives of the warmer parts of America, and many species are
   cultivated. Cosmos bipinnatus and Cosmos diversifolius
   are among the best-known species; Cosmos caudatus, of the
   West Indies, is widely naturalized.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

cosmos
    n 1: everything that exists anywhere; "they study the evolution
         of the universe"; "the biggest tree in existence" [syn:
         universe, existence, creation, world, cosmos,
         macrocosm]
    2: any of various mostly Mexican herbs of the genus Cosmos
       having radiate heads of variously colored flowers and pinnate
       leaves; popular fall-blooming annuals [syn: cosmos,
       cosmea]