Source : Webster's Revised Unabridged Dictionary (1913)

Dahlia \Dah"lia\ (d[aum]l"y[.a] or d[=a]l"y[.a]; 277, 106), n.;
   pl. {Dahlias}. [Named after Andrew Dahl a Swedish botanist.]
   (Bot.)
   A genus of plants native to Mexico and Central America, of
   the order Composit[ae]; also, any plant or flower of the
   genus. The numerous varieties of cultivated dahlias bear
   conspicuous flowers which differ in color.

Source : WordNet®

dahlia
     n : any of several plants of or developed from the species
         Dahlia pinnata having tuberous roots and showy rayed
         variously colored flower heads; native to the mountains
         of Mexico and Central America and Colombia [syn: {Dahlia
         pinnata}]