Bottom Half Strike
In baseball, a pitch that would normally be called a ball, but because the home team is up to bat with a very large lead, the umpire has widened the strike zone so much so that said pitch is called a strike. The pitch is therefore only called a strike in the bottom half of the inning. See top half ball.
"That pitch was over my head, but we're up by 15 and the ump's calling bottom half strikes."