side flash noun 1verb 1forms 3 noun1 •A disruptive electrical discharge between a conductor traversed by an oscillatory current of high frequency (such as lightning) and neighbouring masses of metal, or between different parts of the same conductor. verb1 •Of electricity: to create a side flash.The charge traveled down the aluminum mast, and, not finding a path to ground, it side-flashed, blowing out the boat's hull. — 2010 formsside flashed · side flashing · side flashes