Fash Dash Share definition Flag A fash dash is a fashion disaster, something that looks awful on someone and needs some urgent help asap, from mcivor and saywers preferably ' that girl over there with the fat man pants and the charvy tee? she's a fash dash!' Fash Dash by g-babeeeezzZZzz August 6, 2008 Get the Fash Dash mug.