The Immelmann turn was an aerial maneuver.
In Starfleet Academy, the turn was a demonstration of piloting prowess by cadets. A flight team of cadets would begin with the diamond slot formation, then perfom this turn. (TNG: "The First Duty")
The shrunken USS Rubicon performed a perfect Immelmann turn in 2374 when the runabout approached Worf in the USS Defiant's main engineering. (DS9: "One Little Ship")