Sitchassdown Share definition Flag To combine the words "sit your ass down" into a single fluid word. Originally coined by Samuel L. Jackson in Snakes on a Plane. Screw this, I'm leaving. SITCHASSDOWN! Sitchassdown by Brian Tsai November 25, 2007 0 0 Get merch Get the Sitchassdown mug. Buy Now — $32.95 See more merch