Sharkin (verb) - to knowingly flirt with a person who has a significant other while the significant other is not present, in an attempt to have sexual relations or get the couple to break up.
Person 1: Bro, you need to keep an eye on Jenny.
Person 2: Why?
Person 1: She was at that party with Tom and he was totally sharkin on her.
Billy: hey man are we heading to that girls house?
Chad: Yea but they both have boyfriends.
Billy: are their boyfriends going to be there?
Chad: nope...Fuck it...looks like we're sharkin tonight.