Frosting your cupcake can be defined as when a man shoves his finger into a woman (or man)'s anus, resulting in poop ending up on one's finger. Once the finger is removed, you bake a cupcake and frost it with the unclean finger, and later eating said cupcake.
"Hey Rory, I was totally frosting your cupcake last night"
"Yo, thanks Steve, that was so nice of you to frost my cupcake."
"Anytime, I had fun...frosting your cupcake."

"Word"
by BigSexy123 October 1, 2013
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To cum on a woman's breasts. Preferably B or C cups.
She didn't want frosting in the oven so I was frosting her cupcakes instead.
by collapsing-a-hole March 21, 2010
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To suck or lick someone's balls or genitals on a special occasion.
To frost someone's cupcakes, as in: It's my husband's birthday, I need to go home and frost his cupcakes.
by FunkyArab September 12, 2013
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