Teleport Self is a monster-only spell which causes the caster to randomly teleport a few turns after the spell is cast, much like if it had read a scroll of teleportation. Monsters usually only use this spell after taking significant damage as an emergency escape maneuver.
The following enemies cast Teleport Self:
A number of monsters had Teleport Self removed from their spell sets in 0.17.
Prior to 0.8, Teleport Self was also a level 5 Translocations player spell. It functioned just like any other source of teleportation, and the fact that it took up no inventory space almost made up for the fact that its miscast effects were potentially very lethal (banishment was not uncommon).