An inertia damper is a device that counters or damps the effects of inertia and other forces and motion. The damper does not negate the forces but either absorbs or redirects them by other means. For example, a large suspended mass may be used to absorb several short-duration large forces, and to reapply those forces as a smaller force over a longer period.
The phrase inertial damper is actually misused in science fiction to describe a device that negates inertia and removes it from surrounding mass. It is more properly described as inertia negation.
Inertial compensators are also used in simulators or rides, making them more realistic by creating artificial sensations of acceleration and other movement. The Disneyland ride Space Tours is a fair example of this principle.
There are many types of physical devices that can act as inertia dampers: