This could be attributed to outer appearance or actions such as having a dirty mustache, driving an IROC or wearing an acid washed jean jacket.
Also can be used when referring to a meal, such as a KFC double down, or a super big mac followed by a 20 piece chicken mcnugget.
That meal was greesy!
-- You know it happened, but are damn embarrassed.
-- This person is usually a bit nasty.
-- "The one...? wtf"
-- A name given if you are Chrissy French.