The Collaborative International Dictionary
Tractor biplane
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.