adjective (a)

• of or relating to or characterized by onomatopoeia(adj.pert)

  Synonym:
  onomatopoetic
  

  source: wordnet30
• (of words) formed in imitation of a natural sound(adj.all)

  Example:
  Onomatopoeic words are imitative of noises.
  

  Synonym:
  echoic, imitative, onomatopoeical, onomatopoetic
  Antonym:
  nonechoic
  

  source: wordnet30