Completely Constraint Motion

"TYPES OF CONSTRAINED MOTIONS-

1) Completely Constrained Motion- when the motion between a pair is limited to a definite direction irrespective of the direction of force applied. Example- the motion of a square bar in a square hole.

2) Incompletely Constrained Motion- when the motion between a pair can take place in more than one direction. Example- a circular bar in a circular hole where the bar can either rotate or slide in the hole.

3) Successfully constrained motion- when the motion between a pair is such that the constrained motion is not completed by itself but by some other means. Example- piston reciprocating inside an engine cylinder."

https://sites.google.com/site/mechanicalstuff4u/contents-of-m/theory-of-machines-2/machines-and-mechanisms

A Zen master would unask this question as being unmeaningful.