When a man (or a woman) does something for the hopes that he will receive boob. Usually within the context of money, like paying for dinner so that something sexual will happen after.

A pick me is a woman that is willing to do anything for male approval. She will embarrass or throw other women under the bus to achieve this goal. The unfortunate thing about a pick me is usually the men they are trying to seek approval from are of poor quality and treat women badly, leaving little real benefit for the pick me.