unbelievably adv 1: not easy to believe; "behind you the coastal hills plunge to the incredibly blue sea backed by the Turkish mountains" [syn: {incredibly}, {improbably}, {implausibly}, {unbelievably}] [ant: {believably}, {credibly}, {plausibly}, {probably}] 2: in an unbelievable manner; "he was unbelievably angry" [ant: {believably}]