A very common misspelling of mince pies, often done accidentally when you miss the "n" key because you are in a rush.

Can also refer to a small pie, similar to a mince pie, but instead filled with mouse droppings, served during christmas time to people who give you shite presents.
Tony: Hey, I'm off to get another mice pie, brb.

Dave: Mice pie? WTF?

Tony: SHIT! I mean mince pie! My bad.

Or

Tony: Hey, go give this mice pie to Uncle Freddy

Dave: Yeah! that would totally get him back for buying me another fucking lynx box set this Christmas!
by Mustangboss_429 January 2, 2010
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