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1.
A mustache grown specifically for the viewing pleasure of the Canadian fast paced classic rock band RUSH.
Dude what's with the derty stache?
Man, I'm growing a Rushstache, the Rush concert's in two days!
by NeilPeartInsideMe July 17, 2010
 
2.
A mustache grown specifically for the purpose of fraternity rush. Usually only done by older fraternity men during rush as a sign of experience rushing potential new members.
"Hey man, nice mustache"

"Rushstache kid."
by stonewall230 November 21, 2011