to make stiff.

to become stiff.

to become suddenly tense, rigid, or taut, as in bracing oneself for or drawing back from shock, fear, or displeasure

He stiffened, expecting to hear the worst.

verb

liquefy , loosen , melt

verb

anneal , benumb , brace , cake , candy , cement , chill , clot , coagulate , condense , congeal , crystallize , curdle , firm , fix , freeze , gel , harden , inflate , inspissate , jell , jelly , ossify , petrify , precipitate , prop , reinforce , set , solidify , stabilize , starch , steady , strengthen , tauten , tense , thicken , tighten , bolster