1. n. [Drilling]

The overnight work shift of a drilling crew. Drilling operations usually occur around the clock because of the cost to rent a rig. As a result, there are usually two separate crews working twelve-hour tours to keep the operation going. Some companies prefer three eight-hour tours. The graveyard tour is the shift that begins at midnight. (Pronounced "tower" in many areas.)

See: daylight tour,  drilling crew,  evening tour,  morning tour,  tour