stiffen
v 1: become stiff or stiffer; "He stiffened when he saw his boss
enter the room" [ant: {loosen}]
2: make stiff or stiffer; "Stiffen the cream by adding
gelatine" [ant: {loosen}]
3: restrict; "Tighten the rules"; "stiffen the regulations"
[syn: {tighten}, {tighten up}, {constrain}]