Haha, Look at this definition of 'pot head' that i found on urban dictionary.

Pot Head.

A Habitual user of Marijuana, usually to the point where it interferes with work, family, and school. Pot heads are known for their laid-back attitude, bad memory, encyclopedic knowledge of junkfood, and facination with shiny objects.

Pot heads should not be confused with occasional smokers who are still able to function and fulfill their responsibilities and obligations.