calm down killer Share definition Flag an expression used in america by young adults. Meaning dont freak out, relax, or simmer down. "WTF???"- "calm down killer, its not that big of a deal"-Amy calm down killer by hahahhthisprovesmypointtaber December 10, 2009 0 0 Get merch Get the calm down killer mug. Buy Now — $32.95 See more merch
