Inertia
The tendency of a body to resist acceleration. A body at rest will remain at rest or a body in motion will stay in motion in a straight line unless acted on by an outside force.
Aviation Maintenance Technician Handbook — Powerplant, p. G-15
Also defined in 1 more source
The property of matter by which it will remain at rest or in a state of uniform motion in the same direction unless acted upon by some external force.
Taught in PP-H Quick reference, PP-K Concepts.