Im*prob"a*ble (?), a. [L. improbabilis; pref. im- not + probabilis probable: cf. F. improbable. See Probable.]
Not probable; unlikely to be true; not to be expected under the circumstances or in the usual course of events; as, an improbable story or event.
He . . . sent to Elutherius, then bishop of Rome, an improbable letter, as some of the contents discover.
-- Im*prob"a*ble*ness, n. -- Im*prob"a*bly, adv.
© Webster 1913.