weaken

verb

weak·​en ˈwē-kən 

weakened; weakening

ˈwēk-niŋ, 

ˈwē-kə-  ; weakens

transitive verb

1

: to make weak : lessen the strength of

2

: to reduce in intensity or effectiveness

intransitive verb

: to become weak

weakener

ˈwēk-nər, 

ˈwē-kə- 

noun

Synonyms of weaken

• soften
• injure
• debilitate

Choose the Right Synonym for weaken

weaken, enfeeble, debilitate, undermine, sap, disable mean to lose or cause to lose strength or vigor.

weaken may imply loss of physical strength, health, soundness, or stability or of quality, intensity, or effective power.

a disease that weakens the body's defenses

enfeeble implies a condition of marked weakness and helplessness.

enfeebled by starvation

debilitate suggests a less marked or more temporary impairment of strength or vitality.

the debilitating effects of surgery

undermine and sap suggest a weakening by something working surreptitiously and insidiously.

a poor diet undermines your health

drugs had sapped his ability to think

disable suggests bringing about impairment or limitation in a physical or mental ability.

disabled by an injury sustained at work

Examples of weaken in a Sentence

The disease weakens the immune system.

Some are concerned that the increase in taxes will weaken the economy.

The beams had been weakened by water damage.

efforts to weaken environmental laws

The recent setbacks have not weakened our resolve.

These kinds of contradictions weaken your argument.

The disease causes the immune system to weaken.

The dollar has continued to weaken against the euro.

Lower interest rates have weakened the dollar.

Recent Examples on the Web

Bass, who was politically weakened by her performance during the fire and its aftermath, was already facing more than two dozen challengers looking to oust her in the June 2 primary — the vast majority little known to the public and not expected to pose any threat. —David Zahniser, Los Angeles Times, 6 Feb. 2026

Meanwhile, Moscow escalated its attacks on Ukraine's power grid in an apparent effort to deny civilians power and to weaken public support for the war, while hostilities continued along the roughly 600-mile front line snaking through eastern and southern parts of Ukraine. —Democrat-Gazette Staff From Wire Reports, Arkansas Online, 6 Feb. 2026

The stratospheric warming has weakened the high-altitude vortex slightly, which nudges the polar jet stream and allows some Arctic air to escape. —Brandi D. Addison, Freep.com, 6 Feb. 2026

Bruising policy reversals on a number of unrelated issues last year had already weakened Starmer's authority with his party. —Emmet Lyons, CBS News, 6 Feb. 2026

Word History

First Known Use

circa 1529, in the meaning defined at transitive sense 1

Rhymes for weaken

• beacon
• deacon
• archdeacon
• mohican

Kids Definition

weaken

verb

weak·​en ˈwē-kən 

weakened; weakening ˈwēk-(ə-)niŋ 

: to make or become weak or weaker