When someone is so confident in winning a race or any other competition, that they dance in front of the finish line due to believing they'll cross it first. It is known to not end well for the "winner" as another competitor usually takes the "winner's" place right before they cross the finish line.
As a wise man once said: "winner's dance is a lie. It's the second place dance."
Joinen: "Winner's dance, colon, noun, did not win; but *did* dance. It's an activity actually. It's what you- It's a- It's a verb. It's a thing that you do. Uh, which is to not win, but to dance."