The Collaborative International Dictionary
Inertia \In*er"ti*a\, n. [L., idleness, fr. iners idle. See Inert.]
(Physics) That property of matter by which it tends when at rest to remain so, and when in motion to continue in motion, and in the same straight line or direction, unless acted on by some external force; -- sometimes called vis inerti[ae]. The inertia of a body is proportional to its mass.
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Inertness; indisposition to motion, exertion, or action; lack of energy; sluggishness.
Men . . . have immense irresolution and inertia.
--Carlyle. -
(Med.) Lack of activity; sluggishness; -- said especially of the uterus, when, in labor, its contractions have nearly or wholly ceased.
Center of inertia. (Mech.) See under Center.
Wiktionary
n. 1 The resistance of matter, as when a body at rest is set in motion, or a body in motion is brought to rest, or has its motion changed, either in direction or in velocity. 2 inert; inactivity.
Usage examples of "vis inertiae".
Soon, the Line's own Vis Inertiae having been brought up to speed, they discover additionally that 'tis it, now transporting them.