What it is

A spike is when the quarterback takes the snap and immediately throws the ball hard into the ground, to stop the clock.

In a game

Teams use it near the end of a half when they have no time-outs, to line up for the next play. It costs a down, but saves seconds.

More detail

Officials rule it an incomplete pass, so it is not a penalty. The quarterback has to take the snap first, then throw the ball into the ground right away.