mad lad Share definition Flag An insane dude. Someone who is out of his god damn mind. A guy that did something that nobody would have ever even dared to think of doing. Wow Jacob just drank that entire glass of water, what a fucking mad lad. mad lad by eaozimso February 20, 2017 0 0 Get merch Get the mad lad mug. Buy Now — $32.95 See more merch