Meaning Vehicle Off the Road.
Now replaced by 'Non-Taskworthy'.
For some real fun, take a piece of chalk to the MT square, and write this on a random vehicle or five.
Not all vehicles are road vehicles, and in the case of boats or amphibians just VOR might not tell the whole story. In this case watch out for a VOW sign. It may not be a good idea to nick that particular boat.
With the recent ruling that soldiers DO have human rights, expect more kit to be VOR'ed as HSE go to town on army kit. ie ...