inertia /inur″shə/ [L, idleness] , 1. the tendency of a body at rest to remain at rest unless acted on by an outside force, and the tendency of a body in motion to remain at motion in the direction in which it is moving unless acted on by an outside force. 2. an abnormal condition characterized by a general inactivity or sluggishness, such as colonic inertia or uterine inertia.
