'Tractor' definitions:

Definition of 'tractor'

noun

A wheeled vehicle with large wheels; used in farming and other applications

noun

A truck that has a cab but no body; used for pulling large trailers or vans

From: GCIDE

Tractor \Tract"or\, n. [NL., from L. trahere, tractum, to draw.]
1. That which draws, or is used for drawing. [1913 Webster]
2. pl. (Med.) Two small, pointed rods of metal, formerly used in the treatment called Perkinism. [1913 Webster]
3. a motor vehicle with a powerful engine and large wheels, used to pull farm equipment such as plows, harvesting machinery, etc., over farm land. Smaller forms of farm tractor are completely open, with only a seat for the driver. [PJC]
4. a motor vehicle with a driver's cab and a powerful engine, fitted with a coupling at the rear, and designed to pull a large trailer or semi-trailer on the open highway; -- called also truck tractor. The combination of such a tractor with its trailer is called a tractor-trailer, and is a common form of truck used for commercial shipping of freight. [PJC]
5. (Aviation) A propeller screw placed in front of the supporting planes of an aeroplane instead of behind them, so that it exerts a pull instead of a push; -- called also Tractor screw and Tractor propeller. [Webster 1913 Suppl.]
6. (Aviation) An airplane having one or more tractor propellers; -- called also tractor airplane. [Webster 1913 Suppl.]

From: GCIDE

Tractor airplane \Trac"tor air"plane\, n. (Aviation) An airplane having one or more tractor propellers; -- called also tractor. [Webster 1913 Suppl.]