What does "onomatopoeia" mean?

Onomatopoeia: 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.