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• monkey wrench
  monkey wrench

  noun

  a wrench having an adjustable jaw permitting it to grasp nuts or the like of different sizes.
• monkey-wrench
  monkey-wrench

  verb (used with object)

  to ruin (plans, a schedule, etc.) unavoidably or, sometimes, deliberately.

monkey wrench

¹ American  

noun

1. especially British, adjustable spanner.  a wrench having an adjustable jaw permitting it to grasp nuts or the like of different sizes.

2. something that interferes with functioning; obstacle.

   He threw a monkey wrench into our plans.

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monkey-wrench ² American  

[muhng-kee-rench] / ˈmʌŋ kiˌrɛntʃ /

verb (used with object)

1. to ruin (plans, a schedule, etc.) unavoidably or, sometimes, deliberately.

   The storm monkey-wrenched our plans for a picnic.

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verb (used without object)

1. to prevent, delay, or sabotage industrialization or development of wilderness areas, especially through vandalism.

monkey wrench British  

noun

1. a wrench with adjustable jaws

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Other Word Forms

• monkey-wrencher
  noun

Etymology

Origin of monkey wrench¹

First recorded in 1855–60

Origin of monkey-wrench²

First recorded in 1800–10

Example Sentences

“I’ve learned a lot about what I might get,” she said, “but Mother Nature always has her monkey wrench in hand.”

From Los Angeles Times • Nov. 20, 2025

And part of their idea was you throw a monkey wrench into this process to stop it.

From Salon • Aug. 5, 2023

“The last thing that a booming economy needs is to throw a monkey wrench into a system that we have that is working marvelously well.”

From Seattle Times • Jul. 12, 2023

“To be thrown back into crisis with whatever monkey wrench happens next — I think that would be unfair.”

From Washington Post • Mar. 19, 2022

Even worse, Vonetta had thrown a king-sized monkey wrench into my plans.

From "One Crazy Summer" by Rita Williams-Garcia