A time bubble, or stasis bubble, was a pocket dimension, (PROSE: The Crystal Bucephalus) a four-dimensional sphere (AUDIO: The Eternal Summer) that occurred when an individual met his past or future self under certain circumstances or by intervention of the Time Lords. A bubble resulted in time being frozen save for the individual who caused it or, in reverse, frozen only for the individual who was trapped in it. The bubble would quickly deteriorate and normal time would resume.
The Time Lords captured the King Yrcanos in a time bubble on Thoros Beta, in order to release him at the right time for an attack to the laboratory of Crozier — whose work they wanted to be wiped out. (TV: Mindwarp)
In the court on Space Station Zenobia, the Sixth Doctor and the Valeyard were put in a time bubble for five microspans for consultation. No one outside the bubble were able to see or hear what was going on. (AUDIO: Trial of the Valeyard)
Battle TARDISes could fire time torpedoes to trap targets within stasis bubbles. Karlax and the CIA fired at the War Doctor's TARDIS, temporarily freezing it in a temporal bubble, although this was a bluff by the Doctor since he had upgraded the TARDIS shields. (PROSE: Engines of War)