Synonyms of stiffen

stiffen

verb

ˈsti-fən 

as in to strengthen

to make more harsh, uncompromising, or severe

plans to further stiffen the already onerous requirements for admission to the elite military unit

Synonyms & Similar Words

• strengthen
• harden
• toughen
• harshen

Antonyms & Near Antonyms

• ease
• lessen
• soften
• ameliorate
• moderate

Example Sentences

Recent Examples of stiffen

Offering a 35% incentive aimed at stiffening up jobs here and enticing post-production to relocate to the Golden State, AB 2319 is racing toward a vote in the state Senate by next week once the bill is in final shape. — Dominic Patten, Deadline, 20 Aug. 2026

Softening rather than stiffening when moving through space requires embracing your body’s natural sway and tiny micro-movements, like an ankle wobbling or knee jiggling. — Deborah Vankin, Los Angeles Times, 18 Aug. 2026

Not to mention their unusually flexible blood vessels could also help compensate for stiffening heart tissue. — Melissa Cristina Márquez, Forbes.com, 1 Aug. 2026

Even simple movements can encourage healthy blood flow and keep fascia from stiffening up. — Jennifer Heimlich, Time, 27 July 2026