coup de main - noun
\ˌkü-də-ˈmaⁿ
Definition of coup de main : an attack that achieves complete surprise.

Watch: Taylor Swift and Justin Timberlake perform 'Mirrors' together live.

Last night during the final night of her five night run of 1989 World Tour shows at the Staples Centre in Los Angeles, Justin Timberlake joined Taylor Swift on-stage for a duet of 'Mirrors' together live.

Watch the performance below...