When a person makes a grammatical error when posting something on Facebook. Usually associated with a foreign exchange student in the United States of America.
Luca: Only Etrus have that joy.

Eric: Dude Etrus is one person, not many so it would be has. You just said an Etrus Mistake.

Luca: I just died a little bit on the inside.
by Longdistance4life March 30, 2011
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