What it is

A bomb is a long, high pass thrown deep downfield, usually more than 40 yards in the air.

In a game

The quarterback throws it high enough that the receiver has time to run under it. Fast receivers on a go route or a post are the usual targets.

More detail

The play has a low chance of success but a large payoff. The defense counters it with safeties who stay deep, so offenses often use play action first to draw them closer.