Source : Webster's Revised Unabridged Dictionary (1913)

Impertrubable \Im`per*trub"a*ble\, a. [L. imperturbabilis; pref.
   im- not + perturbare to disturb: cf. F. imperturbable. See
   {Perture}.]
   Incapable of being disturbed or disconcerted; as,
   imperturbable gravity.