Spanish slang, with a literal meaning of "large butt." Nalgón is masculine, nalgona is feminine. It refers to someone who is slow moving. It is often used by drivers when stuck behind such a person.
This nalgón in front of me in the Buick is going to make me late for my date! Oh, it's just some viejito. Figures.
by El Don Diguidi September 11, 2009