inertia

Inertia is the tendency to keep the same motion or walk in a straight line unless something else makes it change direction. (noun)

See inertia in Webster's New World College Dictionary

noun

Physics the tendency of matter to remain at rest if at rest, or, if moving, to keep moving in the same direction, unless affected by some outside force
a tendency to remain in a fixed condition without change; disinclination to move or act

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See inertia in American Heritage Dictionary 4

(ĭ-nûrˈshə)

noun

Physics The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force.
Resistance or disinclination to motion, action, or change: the inertia of an entrenched bureaucracy.

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