An offensive insult used to describe a female that like prefers underweight males, indirectly referencing their intercourse which would resemble a pencil being sharpened.
I saw her in the car with that skeleton-looking kid, you know she's being used as a human pencil sharpener.
When you fall asleep having sex and your penis stays inside the vagina for the whole night. The next morning when you wake up with morning wood still in the vagina is called damp pencil.