Gabrielle Union -- All I Want for Xmas ... IS TO BEAT LEBRON!!!

Forget turtle doves and French hens (who the hell wants a hen?) ... all Gabrielle Union wants for Christmas is for Dwyane Wade and the Miami Heat to CRUSH LEBRON JAMES!!

Union was out in New York Thursday when we asked about her holiday wish list ... and she came back with a not-so-subtle jab at the Heat's #1 defector ... King James.

Of course, the Heat take on the Cleveland Cavaliers on Christmas Day ... and it's clear Union wants her husband to send a message to his old teammate.

There's more ... Gabrielle also reveals who sent the best wedding gift when she tied the knot back in August.