Portal

A portal was a means of travelling across time, space, and/or universes.

The Space-Time Manipulator generated a portal which allowed travel across spacetime. (TV: The Cambridge Spy)

When the Dalek Restoration Empire invaded Islos, the Archivians evacuated the population via a portal in the Archive of Islos. They also used the portal to summon an entity that had agreed to safeguard the populace in exchange for the Emperor of the Restoration. (WC: The Archive of Islos)

During the Last Great Time War, the Time Lords utilised technology that allowed them to open large numbers of blue portals at a time. Although the Tenth Doctor believed that this technology ceased to exist following the Time War, in an alternate timeline where Rassilon granted the Cybermen the means to conquer all of history, the Cybus Cybermen of the 24th century made use of these Gallifreyan portals to transport entire armies of Cybermen onto planets and commence instantaneous invasions; these portals were efficient to the point that the Cybermen's Cyber-Fleets were made redundant.

Sometime during the 24th century of this timeline, the Cybus Cybermen used these Gallifreyan portals to allow an army of thousands of Cybermen to launch an instant full-scale invasion of Sontar, in order to destroy the Last Great Sontaran War Fleet and take control of the Sontarans' cloning factories. The Tenth Doctor was stunned by the Cybermen's use of the portals, to the point that he was nearly killed by a Cyberman that opened a portal directly behind him, although the Sontaran-Prime sacrificed himself to save the Doctor from the Cyberman's energy blaster fire. (COMIC: Supremacy of the Cybermen)