A holo-projection was a hologram used for the purposes of trickery, especially in a starship battle.

Cardassians used sensor ghosts and holo-projections during the Klingon-Cardassian War, a fact that Leskit recalled when comparing the differences in honor between the Cardassians and the Jem'Hadar. (DS9: "Soldiers of the Empire")

The crew of the USS Voyager installed holo-emitters on their ship's hull to fool the Kazon-Nistrim into thinking that they had Talaxian reinforcements during a battle in 2372. (VOY: "Basics, Part I")