SIDRAT

A SIDRAT (pronouced "sigh-drat", not "sid-rat") was a type of space-time vehicle used by the War Lords and built with the assistance of the War Chief, a renegade Time Lord.

Similar to a TARDIS, the SIDRATs were somewhat less-evolved time/space travelling machines. From the outside they resembled featureless rectangle boxes, similar in appearance to a form sometimes used by TARDISes while on Gallifrey. The War Lords employed them both to abduct Human soldiers to the war games, and also to travel back and forth from the game area to their base. (DW: The War Games)

According to one source, the name may have been an acronym for "Space and Inter-Dimensional Robot All-purpose Transporter" (DWN: Doctor Who and the War Games). It is also TARDIS backwards.