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