Source : Webster's Revised Unabridged Dictionary (1913)

Onomatopoeia \On`o*mat`o*p[oe]"ia\, n. [L., fr. Gr. ?; ?, ?, a
   name + ? to make.] (Philol.)
   The formation of words in imitation of sounds; a figure of
   speech in which the sound of a word is imitative of the sound
   of the thing which the word represents; as, the buzz of bees;
   the hiss of a goose; the crackle of fire.

   Note: It has been maintained by some philologist that all
         primary words, especially names, were formed by
         imitation of natural sounds.

Source : WordNet®

onomatopoeia
     n : using words that imitate the sound they denote