D defs.my
Entry 1 sense Webster, 1913

Inertion

· In·er·tion · IPA
01 n. Lack of activity or exertion; inertness; quietude.
  1. 1.
    Lack of activity or exertion; inertness; quietude.[R.]
    “These vicissitudes of exertion and inertion of the arterial system constitute the paroxysms of remittent fever.” — E. Darwin.