a cargo ship designed to carry crude oil in bulk
The oiler supports a vessel's engineer officers in all aspects of engine watch-keeping duties, maintenance and repairs.
an unlicensed member of the engine room staff who oils and greases bearings and moving parts of the main engine and auxiliaries. Most of this work is now done automatically and the oiler merely insures it operates correctly.
An oiler is a ship, also called a tanker, that can carry a liquid cargo of petroleum, or a naval support vessel that carries fuel to other naval ships steaming at sea, and can transfer the fuel during underway replenishment at sea (RAS).
An oiler is one of the most junior crewmember in the engine room of a ship (senior only to a wiper). Their role consists mainly of keeping machinery lubricated.