It is slang for 'i am'.
You:You going out tonight?
Me:ah um
by Josh July 26, 2003
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Performed under the influence.

Bringing your right leg beck as so, ever so slowly, then pounce forward in an aggressive manner towards the sky.
Ah Um Say La Ah Um Say La
And Then you go like this.... (swirl)
by Avi February 28, 2003
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