1) An unsatisfying or non-existent sexual encounter with a woman.
2) A woman who is functionally retarded in terms of sexual skills or performance.
3) The lack of available or attractive women with whom to hook-up.

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.