When someone who is unaware of the meaning of yaharg has the word said, or yelled, to, or at, them. This is typically followed by mild-to-severe confusion and a more pirate oriented attitude.
Guy 1: So I was totally banging this chick when she just fell asleep. It was weird.
Guy 2: Dude, that is weird. You should get that checked out, man.
Guy 1: Yeah, it might've been all the turkey she ate before, thou-
Random guy runs into conversation.
Random guy: YAHARG!!!
Random guy runs away.
Guy 1: What the hell just happened?!?
Guy 2: That guy has been running around yaharg-ing everyone.
Guy 1: Man, I feel like getting drunk and sailing the open seas.
Guy 2: Me too!