compulsion

A compulsion is an urge to do something over and over. A compulsion to check, resist the compulsion, an irresistible compulsion.

In clinical use it names the repeated act in obsessive-compulsive disorder, performed to relieve an intrusive thought — and the relief is brief, which is what keeps the loop turning. In ordinary use it means any strong urge. The other sense is legal: acting under compulsion means being forced, and evidence given under compulsion is treated differently. Note compel, compulsory.