im*prob"a*bly
Webster's Dictionary (GCIDE)
Improbable \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. [1913 Webster]
He . . . sent to Elutherius, then bishop of Rome, an improbable letter, as some of the contents discover. --Milton. -- Im*prob"a*ble*ness, n. -- Im*prob"a*bly, adv. [1913 Webster]