QUICK ANSWER
A dime defense puts six defensive backs on the field instead of the usual four. Teams use it when they expect a pass, trading size near the line of scrimmage for extra coverage.
A dime defense is a defensive package with six defensive backs on the field. A standard defense has four. Teams use the dime when they expect the offense to pass.
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To make room for the two extra defensive backs, two linebackers or defensive linemen come off the field. A common dime lineup has four linemen, one linebacker, and six defensive backs.
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When Teams Use A Dime Defense
The dime is built to stop the pass. Defensive backs are faster than the players they replace, and they are better at covering receivers.
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Teams usually save it for obvious passing situations. Two common examples are third and long, and late in a game when the offense needs to move the ball quickly.
How To Beat A Dime Defense
The easiest way to beat a dime defense is to run the ball. There are two reasons this works.
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The first reason is size. Defensive backs are smaller than linemen and linebackers, so they are easier to block and have a harder time tackling a big running back.
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The second reason is numbers. With fewer defenders near the line of scrimmage, there is less in the way of the run.
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Why Is It Called A Dime Defense?
The name comes from the nickel defense, which uses five defensive backs. A nickel is worth five cents, so the name fits the fifth defensive back, often called a nickel corner.
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The dime adds one more defensive back, for two extra in total, and two nickels make a dime. The sixth defensive back is often called the dimeback.