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.]