Often confuzed with "masturbation"
It has nothing to do with that, though it may be used unwisely by some.
It is used to de-compliment someone or make fun of how they look.

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.