throw a spanner in the works
Definition from Wiktionary, a free dictionary
[edit] English
[edit] Verb
- (idiomatic) (UK) To be a problem, dilemma or obstacle, something unexpected or troublesome.
- Half way through the production of Macbeth, the director found that the stage was smaller than he expected. This really threw a spanner in the works.
[edit] See also
- monkey wrench (US)

