A Skuzzy Onion is someone who is nasty and a scrub. Skuzzy Onion can be saw as wearing dirty clothes, Smelling like sex (B.O or any bodily fluid/Odor) and someone who does not take care of themselves.
John: Ew, Whats the smell?
Steve: Sorry dude, I didnt shower yet.
John: Dude your such a skuzzy Onion.
Valeria: Wheres Amber?
Ashley: Oh, you mean Skuzzy Onion?
Valeria: How is she a Skuzzy Onion?
Ashley: Because when she slept over my house last night she smelled like pure sex.