E.P.I.A.R. is an acronym for the phrase, "Every post is a repost!" It is commonly used among the internets to point out when something has already been posted, often many times before.
Original Post op: Hey guys, take a look at this video about a guy named Leeroy Jenkins! It's really funny, you should really watch it!
Second Poster: EPIAR!
Third Poster: EPIAR!
Fourth Poster: EPIAR!