Top Definition
To cruise down the street in your car with the window rolled down with you arm hanging out the window making your muscles look bigger than they actually are.
Let's go fat arm it down mendo.
by DaLumberjack June 17, 2008
when you lift your arm up and there is fat jiggling to and fro.
or you are just obese and everything about you is fat, including your arms.
wayne, "dont look now! that lady has some serious fatarm."
jimbo, "damn bro, that lady fat."
by jess October 16, 2004
A lesbian rower who is known to sleep with someones boy friend...also can be called ant farm or dykleznowkbi or horse face bird nose
Rachel is a fat arm.
by Young Nak and Lil' Ash Ass October 22, 2006

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