1. A thin pedophile mustache usually on a teenage boy that can barely grow facial hair. Made popular by a dude named Goose who has a pedophile mustache.
2. A mustache on a dude named Goose.
Look at that odd GooseStache.
I am going to grow a GooseStasche.
When are you going to cut off your GooseStache
A moustache that a teenager (or adult) grows in an attempt to look cool, but makes them look like a goon. In some cases the moustache is not filled in all the way or is badly groomed.
He thinks he looks cool with his goonstache, but it looks like dirt under his lip