When a person's hair looks like a slug/ is the same shape as a slug.

A person with an outwardly dominant, masculine, or aggressive personality, but who also enthusiastically takes on the submissive or "bottom" role in the bedroom.

One with so much shit between his/her ears they can't form rational thoughts or predictable behavior.

Someone with a Mohawk on their head, usually un-gelled/flat and/or scruffy.

Looks like a slug on their head.