Source : Webster's Revised Unabridged Dictionary (1913)

Dicotyledon \Di*cot`y*le"don\, n. [Pref. di- + cotyledon.]
   (Bot.)
   A plant whose seeds divide into two seed lobes, or
   cotyledons, in germinating.

Source : WordNet®

dicotyledon
     n : flowering plant with two cotyledons; the stem grows by
         deposit on its outside [syn: {dicot}, {magnoliopsid}, {exogen}]