By most definitions, onomatopoeia means the use of words that imitate sound. It can also refer to the property of such words. According Wikipedia, onomatopoeia can be a countable noun, so kaboom would be an onomatopoeia, and the plural would be onomatopoeias. The adjective onomatopoeic is synonymous with echoic or imitative. The word comes from Greek and roughly means “name-making”, which makes sense because the sound makes the meaning. Onomatopoeia is found everywhere: in poetry, children’s books, comics, literature, advertisement, art, in everyday conversation and on the web.
via Written Sound