'Imperturbable' definitions:

Definition of 'imperturbable'

From: WordNet
adjective
Not easily perturbed or excited or upset; marked by extreme calm and composure; "hitherto imperturbable, he now showed signs of alarm"; "an imperturbable self- possession"; "unflappable in a crisis" [syn: imperturbable, unflappable]

Definition of 'Imperturbable'

From: GCIDE
  • Imperturbable \Im`per*turb"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. [1913 Webster]