Basically a dick that is seen as inferior to the majority of the world. A penis so pathetic that anyone who lays eyes on it would laugh and call it a "scrub dick".
Noun/Adjective/Pronoun, the use of this word are endless. Basically someone/something/description of the worse kind of scum imaginable. Worse than the old shit stain around your toilet bowl that has been encrusted over by multiple shits. Calling someone a fuck head is a compliment compared to calling someone this word. The leftover dried up crusty cum.