When a person without a mustache gives a person with a mustache some sort of a sign of respect for his sweet stache.
Originated in 2001, by Krampack, as a way to salute El Stachio when arriving at his well. The original salute consisted of sliding one's index finger slowly across their upper lip, in an arched manner.
"That guy has been rocking his stache since High School, so I always give him a proper Stache Salute."
"I always give him mad props with a Stache Salute."