Greasy Gus Share definition Flag Any man who is very dirty in appearance. He usually dresses slovenly and always drives a pick-up truck that is at least 30 years old. Man, did you see that guy that just left. He's totally a Greasy Gus! Greasy Gus by Mark 18 May 21, 2007 0 0 Get merch Get the Greasy Gus mug. Buy Now — $32.95 See more merch