Linguistic Tinkering

Onomatopoeia is a very disappointing word.  Referring to a word that imitates a sound, onomatopoeia is a colorful rhetorical device, examples of which include "splash," "honk," "meow," and "wombat" (because, let's face it, when you hear the word 'wombat,' you immediately get a mental image of what the word sounds like):

Here's my problem, though: Shouldn't the word for "a word that imitates a sound" be an example of onomatopoeia?  In other words, I think the word for a word that sounds like the thing it describes should be something like 'wordthatsoundslikethethingitdescribes.'

Somebody get on that, please.