n. [ L. imperturbatio. ] Freedom from agitation of mind; calmness; quietude. W. Montagu. [ 1913 Webster ]
n. [ L. perturbatio: cf. F. perturbation. ]
a. Of or pertaining to perturbation, esp. to the perturbations of the planets. “The perturbational theory.” Sir J. Herschel. [ 1913 Webster ]