A very unattractive, creepy guy at bar, who lurks, watches, and looks for women to hit on. He is also the unattractive, creepy guy on the dance floor who will attempt to dance with you multiple times and never get the hint that you don't want to.
"Oh my god, that creepy guy keeps staring at us. What a skeevester!"
"That guy would not stop trying to dance with me. He is a total skeevester!"
Genereally means bastard, but not in the literal term. Just an annoying person who you don't like or who has donesomething stupidly irritating. Most comonly known from Mean Girls.