Definition of inertial in US English:



  • 1Relating to or arising from inertia.

    • ‘Another way of understanding the situation is to remember the equivalence Einstein explained between gravitational and inertial forces.’
    • ‘The interesting thing is that, physically, no difference has been found between gravitational and inertial mass.’
    • ‘In Newton's theory, all three of these masses - the inertial mass, the active and passive gravitational masses - are equivalent.’
    • ‘If its axis were to be suddenly shifted from its normal inclination, inertial forces produced in such a change would literally tear the earth apart.’
    • ‘Einstein warmed to the idea that the gravitational field of the rest of the Universe might explain centrifugal and other inertial forces resulting from acceleration.’
    1. 1.1 (of navigation or guidance) depending on internal instruments which measure a craft's acceleration and compare the calculated position with stored data.
      • ‘The missile has new GPS / INS (global positioning / inertial navigation) guidance and kinetic warhead.’
      • ‘The aircraft's navigation system includes an integrated inertial navigation and global positioning INS / GPS system.’
      • ‘A rocket's inertial guidance system measures acceleration along three principal directions.’
      • ‘The aircraft uses a Honeywell inertial navigation system.’
      • ‘Inside is a guidance control unit with inertial navigation and global positioning systems.’
    2. 1.2 (of a frame of reference) in which bodies continue at rest or in uniform straight motion unless acted on by a force.
      • ‘Mach had stated a principle that local inertial frames of reference were determined by the large scale distribution of mass in the universe.’
      • ‘The rest-mass of a body is the inertial mass of that body when it is at rest relative to an inertial frame.’
      • ‘Simple laws apply to constant motion in a straight line (an inertial frame of reference).’
      • ‘Photons, according to the special theory of relativity, move in vacuum with the same speed in all inertial frames of reference.’
      • ‘A reference frame in which star motion is ignored and the stars are assumed to be at rest is approximately an inertial reference frame and is often adequate for many purposes.’