Wormhole

A wormhole was a passage which links two separate points in space-time, usually serving as a shortcut between those two points.

The Swarm traveled from planet to planet through wormholes they created. One of these linked the planets San Helios and Earth, through which the passengers of a London bus (including the Doctor and Lady Christina de Souza) arrived. The wormhole was eventually closed by Professor Malcolm Taylor before most of the Swarm could get through, thus saving the world. (DW: Planet of the Dead). These particular wormholes created by the Swarm contain high amounts of dangerous energy, instantly incinerating anything that passes through it - the only way to survive the journey through the wormhole is a metal shield (even a damaged vehicle will suffice) enclosing the occupants. The Swarm alone could travel through their wormholes due to their metal exoskeletons.

The Shalka were capable of converting black holes into wormholes. (WC: Scream of the Shalka)

During the Millennium War, the Osirians stopped the Mad Mind of Bophemeral from creating a wormhole in the Horsehead Nebula, which would have killed quintillions. (PDA: The Quantum Archangel)

Phobos had a wormhole located on its surface. (BBCR/BFA: Phobos)