A guy at a party or a bar that is out specifically to get laid and hits on women. He is usually drunk. He doesn’t want a girlfriend, a friend or a relationship- he only wants one thing. So he focuses on one girl who seems like a good target... She is usually an acquaintance or "a friend of a friend," a.k.a. Fresh Meat. He hovers over her trying to impress her with funny stories, insightful ideas and casually mentioning his good qualities. He buys her drinks to get on her good side and perhaps increase his chances of getting laid. He agrees with everything she says, compliments her and calls down other men to make himself look good. He puts his arm around her to show other guys he is targeting her and any interference is met with passive aggression. He leads her away from the group and tries to take her home with him.
A Poon Vulture is basically any drunk guy, swinger or slut that is looking for a one night stand. Most examples are men from teen-comedies who are on a quest to pick up women.