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

Those at higher risk for severe pneumonia and sepsis include older adults and smokers, as well as those with chronic lung disease, diabetes, weakened immune systems or recent viral infections. —Melissa Rudy, FOXNews.com, 23 May 2026

Eleven Indiana House districts – three of them in Porter County – have been targeted by the Democratic Legislative Campaign Committee and the Indiana House Democratic Caucus as crucial for weakening the Republican supermajority in the Indiana General Assembly. —Doug Ross, Chicago Tribune, 23 May 2026

Annual weeds typically won’t regrow, and perennials are weakened. —Nadia Hassani, The Spruce, 23 May 2026

However, their tunnels can weaken foundations and undermine the stability of the soil under your home, says Jason Burkhart, managing director at Critter Control. —Helena Madden, Martha Stewart, 23 May 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