Main entry: stiffen
Definition: make stiff or stiffer
Usage: Stiffen the cream by adding gelatine
Main entry: stiffen
Definition: become stiff or stiffer
Usage: He stiffened when he saw his boss enter the room
Main entry: stiffen, tighten, tighten up, constrain
Definition: restrict
Usage: Tighten the rules; stiffen the regulations