Deep Strike
Deep Strike is a Universal Special Rule in Warhammer 40,000 representing the ability of some units to enter battle directly, as opposed to coming in from an edge. This generally involves dropping in from above, by such means as Drop Pods, grav-chutes (favored method of Elysian Drop Troops), or just flying in, though some units drill in from below (such as the Tyranid Mawloc or Imperial Guard's Hades Breaching Drill) and others teleport or otherwise warp in (like Space Marine Terminators and Chaos Daemons).
The term seems to be used in-universe, as Commander Indrick Boreale describes Steel Rain as involving "multiple, simultaneous, and devastating defensive Deep Strikes."