Definition of Audible

What does the term "Audible" mean in the game of football? What is meant by an "audible"?

In football, an audible occurs when a quarterback changes a play while the team is set and ready to run a play.

Quarterbacks have a tremendous amount of responsibility in the game of football, and one of those responsibilities includes reading defences.

A quarterback is expected to observe the formation of the defence prior to snapping the ball, and relay audibles to the rest of his team if he thinks that the play should be changed.

For instance - let's say that the offensive team calls for a run play and the team lines up.

Prior to snapping the ball, the quarterback notices that the defence appears to be preparing for a blitz.

Instead of snapping the ball, the quarterback yells something out - "Omaha Omaha Nebraska!"

The offensive players know what this means - a bubble screen to the running back.

The ball is snapped and the offensive team runs a screen, thwarting the blitz of the defensive side.