Inop is short for "inoperable", which means the vehicle does not run or operate. This is a term commonly used in auto auctions, auto transport, and in the automotive industry in general. .It is used describe the condition of a vehicle that cannot be driven. Some also call in Non-Op when referring to a DMV status.
Inoperable vehicles in regards to auto transport will usually need to roll and steer. If the vehicle does not roll and steer, it will be necessary for the location to have a fork lift or another tow truck present to lift the vehicle on to the carrier and once again off the car carrier.
Some car carriers are equipped with a winch. However, car carriers are not usually willing to drag and scrape vehicles that don't roll. This can further damage the vehicle and damage their truck. A typical winch will also not be able to pull a vehicle being dragged.