monkey wrench

US: (mung′kē rench′)

WordReference Random House Learner's Dictionary of American English © 2026

ˈmon•key ˌwrench, n. [countable]

1. Building a wrench having a movable opening that can be adjusted for grasping nuts of different sizes.
2. something that interferes:
   That throws a monkey wrench into our plans.

WordReference Random House Unabridged Dictionary of American English © 2026

mon′key wrench′, 

1. Building Also called,[esp. Brit.,] 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.
• 1855–60

mon•key-wrench  (mung′kē rench′), v.t. 

1. to ruin (plans, a schedule, etc.) unavoidably or, sometimes, deliberately:
   The storm monkey-wrenched our plans for a picnic.

v.i. 

2. to prevent, delay, or sabotage industrialization or development of wilderness areas, esp. through vandalism.

mon′key-wrench′er, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

monkey wrench noun

1. a wrench with adjustable jaws