Meaning of inertial system

iner'tial sys'tem

Pronunciation: [key]
— Physics. Physics.
  1. a frame of reference in which a body remains at rest or moves with constant linear velocity unless acted upon by forces: any frame of reference that moves with constant velocity relative to an inertial system is itself an inertial system. Also calledCf. law of motion.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.