The Yeager loop was a starship maneuver that was typically performed by five ships.
The ships performing the maneuver began in a diamond slot formation. They then climbed and looped backwards at a steep angle and at the peak of the loop, turned over and accelerated in a new direction. This maneuver was known as the Immelmann turn.
The maneuver was performed by Nova Squadron in 2368, aboard their Academy trainer craft, as a prelude to their infamous attempt at the Kolvoord Starburst. (TNG: "The First Duty")
According to Star Trek Encyclopedia, 3rd ed., p. 571, the Yeager loop was named after one of Chuck Yeager's most famous flight maneuvers.