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

Graham's aorta, at 71, tore, a dissection along a wall stiffened by decades of what the medical examiner called arteriosclerotic cardiovascular disease. — Dr. Céline Gounder, CBS News, 13 July 2026

Group 1 is pulmonary arterial hypertension, a rare and severe version that occurs when blood vessels in the lungs narrow and stiffen. — Elizabeth Cooney, STAT, 26 June 2026

Pulisic played a dynamic first half in the Americans' historic 4-1 victory over Paraguay to open their home World Cup nearly two weeks ago, but the AC Milan midfielder came off at halftime after an injury from training stiffened up. — ABC News, 24 June 2026

For seven-and-a-half years, Ladd had dealt with idiopathic pulmonary fibrosis (IPF), a progressive lung disease that stiffens and scars the lungs. — Helen Carefoot, Flow Space, 24 June 2026