look up any word, like eiffel tower:
A canon cop is a person who insists you adhere to the intricate details of a particular intellectual property's canon when discussing it, writing fanfics about it, ect.
Bill: Oh, I remember Terminator 2, wasn't that the movie with the robot made out of liquid steel?

Mike: Excuse me, I believe you mean it was made out of a mimetic polyalloy, and it was no ordinary robot but rather an advanced T-1000 Terminator. Furthermore-

Bill: Shut up! Nobody cares, you canon cop!
by Geldon August 13, 2011