1. to damage or change (something) in a way that ruins it or prevents it from working properly

1. All the plans for the party were going yo until Masha threw a monkey wrench into the works.

2. When John suddenly refused to help us, he really threw a monkey wrench in the works.

3. The storm threw a monkey wrench into their plans for a picnic.

4. I don’t want to throw a monkey wrench in the works, but have you checked your plans with a lawyer?