Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impossĭbĭlis (inp-), e, adj. [2. inpossibilis], impossible (post-Aug.): impossibile aut potius infinitum est, Quint. 5, 10, 18: impossibilia aggrediantur, id. 5, 13, 34: nihil impossibile arbitror, App. M. 1, p. 111: ut Herculi quasi impossibile imperaverit, ut, etc., Just. 2, 4; App. Dogm. Plat. 3, p. 38: impossibile est, ut alveus fluminis publici non sit publicus, Dig. 43, 11, 1 med.: condicio, Gai. Inst. 3, 98.