A symbol that ends a proof, usually mathematical. QED and w^5 are the most common EOP symbols. Many people make up their own; mine is an Interstate 99 shield with a circle with a line thru it around it, representing my dislike of Interstate 99. On E2 I must approximate it (9/9). Others I have seen are a triangular gastropod and 1=2; the latter is not recommended on a test though.