COS Share definition Flag Comfort Over Swag- Usually given to the guy who'd rather wear sweatpants than jeans out. "John really believes in COS, dude." "Yeah he was wearing sweatpants and a sweatshirt to the club last night." COS by COS pro June 7, 2013 0 0 Get merch Get the COS mug. Buy Now — $32.95 See more merch