In American football, the dime defense is a defensive alignment that uses six defensive backs

Defensive back

In American football and Canadian football, defensive backs are the players on the defensive team who take positions somewhat back from the line of scrimmage; they are distinguished from the defensive line players and linebackers, who take positions directly behind or close to the line of...

. It is usually employed in obvious passing situations.

The formation usually consists of six defensive backs, and has either four down linemen and one linebacker

Linebacker

A linebacker is a position in American football that was invented by football coach Fielding H. Yost of the University of Michigan. Linebackers are members of the defensive team, and line up approximately three to five yards behind the line of scrimmage, behind the defensive linemen...

, or three down linemen and two linebackers. The formation is vulnerable to running plays, but usually only employed when an offense can scarcely afford to run even for a good gain, either because of the great distance needed to get a first down, a lack of time, or both.

A dime defense differs from the nickel

Nickel defense

In American football, a nickel defense is a defensive alignment that uses five defensive backs, of whom the fifth is known as a nickelback. Although the modern definition of the term encompasses all formations featuring five defensive backs, the original and still most common form of the nickel...

 in that it adds yet another defensive back to the secondary. This sixth defensive back is called a "dime back" (DB). The defense gets its name because a dime is worth two nickels in American currency.