What is "tractor screw"

Tractor screw \Tractor screw\ or Tractor propeller \Tractor propeller\ (Aviation) A propeller screw placed in front of the supporting planes of an airplane instead of behind them, so that it exerts a pull instead of a push. Hence,

Tractor monoplane,

Tractor biplane, etc. This is the most common arrangement for propellers on modern airplanes.

Tractor \Tract"or\, n. [NL., from L. trahere, tractum, to draw.]

1. That which draws, or is used for drawing.

2. pl. (Med.) Two small, pointed rods of metal, formerly used in the treatment called Perkinism.

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.

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.

5. (Aviation) A propeller screw placed in front of the supporting planes of an a["e]roplane instead of behind them, so that it exerts a pull instead of a push; -- called also Tractor screw and Tractor propeller.

6. (Aviation) An airplane having one or more tractor propellers; -- called also tractor airplane.