Mechanism definition: an assembly of moving parts performing a complete functional motion, often being part of a large machine; linkage.. See examples of MECHANISM used in a sentence. Learn about the definition, types, and analysis of mechanisms in engineering. A mechanism is a device that transforms input forces and movement into a desired set of output forces and movement, using links and kinematic pairs. mechanism , in mechanical construction, the means employed to transmit and modify motion in a machine or any assemblage of mechanical parts. The chief characteristic of the mechanism of a machine is that all members have constrained motion; i.e., the parts can move only in a determinate manner relative to one another. The nature of these relative motions is determined largely by the number of parts and the way in which they are connected. MECHANISM definition: 1. a part of a machine, or a set of parts that work together: 2. a way of doing something that is…. Learn more.