Clag Share definition Flag Clag is the a northern word used in place of punch and hit. is used generally after alcohol consumption and usually when in the wrong! He is such a cheeky fucker he is, am gonna have to clag him if he doesn't watch his gob, like! Clag by John Christal December 9, 2008 0 0 Get merch Get the Clag mug. Buy Now — $32.95 See more merch