1)The formation of words in imitation of natural sounds
2)An imitative word
3)The selection and use of such words
4)Simply, words that sound like what they are such as...
What happens when you urinate on your mother and then tell people about it.
"Yesterday got really weird. It was Thanksgiving. And, I'm Italian. So, I had a lot of vino to drink with the ol' family. And then, before I knew it, I made an 'onomatopoeia.' Em-barrassing!"