The use of words to imitate non-verbal sound, for example 'hiss', 'bang', 'pop' or even 'kerpow'.
Citation:
Editors. "Onomatopoeia".
The Literary Encyclopedia. First published 01 November 2001
[http://www.litencyc.com/php/stopics.php?rec=true&UID=793, accessed 22 May 2013.]