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

Echosmith and Taylor Swift performing 'Cool Kids' together live.

Echosmith joined Taylor Swift on-stage during her 1989 Tour show in Philadelphia this past weekend, as her special-guest to perform 'Cool Kids' together live.

Watch the performance below...

P.S. Click HERE to read our latest interview with Echosmith.