Ack Stash Share definition Flag An acne mustache; having acne on one's upper lip. Guy: Have you kissed Jessica yet? Boyfriend: Hell no... Have you seen her ack stash? Guy: Oh... Gross. Ack Stash by Jaja A January 10, 2009 0 0 Get merch Get the Ack Stash mug. Buy Now — $32.95 See more merch