stiffen

verb

stiff·​en ˈsti-fən 

stiffened; stiffening ˈsti-fə-niŋ 

ˈstif-niŋ

transitive verb

: to make stiff or stiffer

intransitive verb

: to become stiff or stiffer

stiffener

ˈsti-fə-nər 

ˈstif-nər

noun

Synonyms

• harden
• harshen
• strengthen
• toughen

Examples of stiffen in a Sentence

She stiffened when he grabbed her shoulder.

The dogs stiffened in alarm.

The law would stiffen penalties for tax evasion.

Recent Examples on the Web

Spritzing the end of the thread with hairspray will stiffen it just enough to be able to be threaded more easily, but keeps enough flexibility to be used. —Kaitlyn Yarborough, Southern Living, 5 Jan. 2025

Restrictive cardiomyopathy: Another rare type, this causes heart muscles to stiffen, which in turn prevents the heart’s ventricles from filling with enough blood to pump throughout the body. —Elizabeth Millard, TIME, 18 Dec. 2024

But the Ravens defense stiffened at the right time, sacking Wilson with defensive tackle Nnamdi Madubuike delivering a crunching sack on a third-down play to force a punt as the third quarter came to an end. —Kyle Feldscher, CNN, 12 Jan. 2025

The schedule stiffens now, starting with Ja Morant and the Memphis Grizzlies at home on Saturday. —Jon Krawczynski, The Athletic, 10 Jan. 2025

Word History

First Known Use

15th century, in the meaning defined at transitive sense

Kids Definition

stiffen

verb

stiff·​en ˈstif-ən 

stiffened; stiffening -(ə-)niŋ 

: to make or become stiff or stiffer

stiffener

-(ə-)nər 

noun