torque
1. a necklace or armband made of twisted metal, worn esp by the ancient Britons and Gauls
2. any force or system of forces that causes or tends to cause rotation
3. the ability of a shaft to cause rotation
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
Torque
The product of a force and its perpendicular distance to a point of turning; also called the moment of the force. Torque produces torsion and tends to produce rotation. Torque arises from a force or forces acting tangentially to a cylinder or from any force or force system acting about a point. A couple, consisting of two equal, parallel, and oppositely directed forces, produces a torque or moment about the central point. A prime mover such as a turbine exerts a twisting effort on its output shaft, measured as torque. In structures, torque appears as the sum of moments of torsional shear forces acting on a transverse section of a shaft or beam. See Couple
McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
torque
[tȯrk] (mechanics)
For a single force, the cross product of a vector from some reference point to the point of application of the force with the force itself. Also known as moment of force; rotation moment.
For several forces, the vector sum of the torques (first definition) associated with each of the forces.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
torque
That which tends to produce rotation; the product of a force and a lever arm which tends to twist a body, as the action of a wrench turning a nut on a bolt.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
torque

Rotation of propeller produces torque.

The illustration shows torque of a propeller. Here 2πrn is the rotational velocity. The direction of the torque is opposite to that of the direction of rotation of propeller.
The moment of force or combination of forces that tends to produce rotational motion. Torque is the counterforce against the engine force that drives a propeller or rotor. It is measured by multiplying the force by its perpendicular distance from the turning point.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved