Synonyms of stiffen in English:

stiffen


See definition of stiffen

verb

1‘stir until the mixture stiffens’

SYNONYMS
become stiff, thicken
set, become solid, solidify, harden, gel, congeal, coagulate, clot

2‘she stiffened her muscles’

SYNONYMS
become rigid, become stiff, make rigid, make stiff, tense, tense up, tighten, tauten
rigidify
technical ankylose
ANTONYMS

relax

3‘attempts to intimidate them have only stiffened their resolve’

SYNONYMS
strengthen, harden, toughen, fortify, give strength to, reinforce, brace, steel, give a boost to
ANTONYMS

weaken