To disrupt, foil, or cause problems to a plan, activity, or project. Primarily heard in UK. We had everything in line for the party, but having the caterer cancel on us at the last minute really threw a spanner in the works!It'll really throw a spanner into the works if the board decides not to increase our funding for this project.
(British & Australian) alsoput/throw a (monkey) wrench in the works (American)
to do something that prevents a plan or activity from succeeding We were hoping to get the project started in June but the funding was withdrawn so that rather threw a spanner in the works.The sudden withdrawal of the guest speaker really threw a monkey wrench in the works.