Cosh Share definition Flag To lick a pregnant person's vagina. Usually, you end up with a mouth full of mucas. "DUDE! I coshed my girlfriend last night," "EW! How nasty was it?" "Pretty bad man, pretty bad." Cosh by sillybillyfillykillymilly December 23, 2008 0 0 Get merch Get the Cosh mug. Buy Now — $32.95 See more merch