Obusor
The stupid grin you get when you know you're going to beat your friend at a game and you're already winning.
He was winning the game, but I knew I was going to beat him and I had the stupidest grin.
She was ahead in the game, but I knew I was going to win and I just smiled like a fool.
He was winning the race, but I knew I was going to beat him and I had the biggest grin.