Poem In My Pocket

I've got a poem in my pocket
neither a limerick nor Nantucket
it's not a haiku or a sonnet
no children will be taught upon it
no triolet or villanelle
(there's no refrain, that's how you tell)
It's not an ode or a cinquain
I haven't written it for gain
and most of all, it's not free verse
though if done well, I'm not averse