1. 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.
Pronunciation: (mung'kē-rench"), [key]
to ruin (plans, a schedule, etc.) unavoidably or, sometimes, deliberately: The storm monkey-wrenched our plans for a picnic.
to prevent, delay, or sabotage industrialization or development of wilderness areas, esp. through vandalism.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.