A twisting couple is one in which the couple's plane is parallel to the cross-sectional plane of the member.
A suitable word would be force pair of pure instant. It causes rotation without translation, or, to put it another way, without acceleration of the center of mass.
In rigid body mechanics, force couplings are free vectors, which means their effects on a body are independent of the site of application.
The resultant moment of a pair is called a torque. This should not be confused with the phrase torque, which is a physics synonym for the moment. On the other hand, torque is a form of the moment.
In solid mechanics, torsion is the twisting of an object generated by applied torque.
Torsion is represented in Pascal (Pa), a SI unit for newtons per square metre, or in pounds per square inch, and is measured in newton metres (Nm) or foot-pound force (psi).