jackmans - A hairball that grows at the back of your neck, like your he

A hairball that grows at the back of your neck, like your head is trying to grow a beard in the wrong place.

I have a jackman, and it's bigger than my head.

My brother has a jackman, and it looks like a squirrel lives in his hair.

My mom says my jackman is going to grow into a full head of hair, and I'm going to look like a monkey.