What does "spanner in the works" mean? Is it an idiom?

Native speaker’s answer
Rebecca
That's correct! To "throw a spanner in the works" means to disrupt, interrupt, or prevent something from running smoothly or going as planned. Ex: I had planned to go back to school, but an unexpected pregnancy threw a spanner in the works. Ex: The sudden rainstorm threw a spanner in the works for the organizers of the outdoor concert.