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The Collaborative International Dictionary of English v.0.48 (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.]


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