\DAY-uhs-eks-MAH-kuh-nuh; -nah; -MAK-uh-nuh\, noun: 1. In ancient Greek and Roman drama, a god introduced by means of a crane to unravel and resolve the plot. 2. Any active agent who appears unexpectedly to solve an apparently insoluble difficulty.
I find it mildly amusing that people complain about deus ex machina endings in film without knowing the correct term for such annoying contrivances.