A time-trance was a state of temporal suspension, in which an individual living being or beings were unable to move. These trances could be induced by temporal stasis fields generated by a temporal stasis machine.
When the Cybermen put a stasis field around Centuria Central, Jayne Kadett was placed into a time-trance. The Tenth Doctor avoided this fate because he was a Time Lord, and so was immune to the field's effects. (COMIC: Time of the Cybermen)