Antonyms of adv believably

1 of 2 senses of believably

Sense 1
believably -- (in a believable manner; "he acted believably sincere")
       Antonym of unbelievably (Sense 2)
      => unbelievably -- (in an unbelievable manner; "he was unbelievably angry")
       Antonym of unbelievably (Sense 1)
      => incredibly, improbably, implausibly, unbelievably -- (not easy to believe; "behind you the coastal hills plunge to the incredibly blue sea backed by the Turkish mountains")

Synonyms of adv believably

2 senses of believably

Sense 1
believably -- (in a believable manner; "he acted believably sincere")

Sense 2
credibly, believably, plausibly, probably -- (easy to believe on the basis of available evidence; "he talked plausibly before the committee"; "he will probably win the election")