To become thick or thicker.To become deeper or heavier; gain bulk.Of a liquid, to approach more nearly a state of solidity; gain firmer consistency; also, to become turbid or cloudy.To become dark or obscure; specifically, of the weather, etc., to become misty or foggy.To grow more intense, profound, animated, intricate, etc.; become complicated.To gain in number or frequency; hence, to crowd; throng.To become indistinct.To make thick or thicker.To increase in depth, or distance between opposite surfaces; hence, figuratively, to make stouter or more substantial; strengthen.Of liquids, to increase the consistency of; inspissate: as, to thicken gravy with flour; also, to render turbid or cloudy.To obscure with clouds or mist; befog.To make more numerous or frequent; redouble: as, to thicken blows.n. A spelling of thick 'un (which see, under thick, a.).