1) N-COUNT A spanner is a metal tool whose end fits round a nut so that you can turn it to loosen or tighten it. [mainly BRIT]
(in AM, usually use , monkey wrench)
2) PHRASE: V inflects If someone throws a spanner in the works, they prevent something happening smoothly in the way that it was planned, by causing a problem or difficulty. [BRIT]

A bad result is sure to throw a spanner in the works.

(in AM, use throw a wrench, throw a monkey wrench)

English dictionary. 2008.