smash mallow Share definition Flag when u shove a ton of marshmallows up your rectum and out comes a chocolate covered smashed blueberry. but it's not really blue, it's brown as fuck eh brah u try that smash mallow last night?oh hell no homie that shit nasty as fuck smash mallow by brown mallow 1 2 3 4 March 8, 2017 Get the smash mallow mug.