An unlicensed or on-the-sidemechanic that you go to when you can't afford to go to a real mechanic. Often used when the job is simple, or you no longer want to dump money into your very old car.
Can also be applied to a halfway knowledgable person in any field (ie: computer repairs, home repairs, gender reassignment)
"I took my car to this grease monkey I know and he screwed up my tranny. That'llteach me to stop being cheap."
Someone who deliberately does not wash their hair reguarly and is regarded by others as a greasy skett. Hair smells and dandruff flakes are apparent they are not pleasent to look at.
Worker #1: She got the biggestass licking in the world in the weekly newsletter.
Worker #2: She must be giving the boss grease monkeys in the lactation room.