Top Definition
The phenomenon that occurs when an overly large person sits next to you on a bus, train, or plane and their ass flows under the armrest into your seating area.
God, that flight was absolutely miserable; not only was it a small plane, but that big girl next to me was totally guilty of asscroachment since half of her butt cheek was in my seat.

Don't some airlines charge obese people for two seats to avoid asscroachment on other paying passengers.
by Bubba Adbul Ledbetter November 16, 2009

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