unbelievable

From un- +‎ believable.^[1]

• IPA^(key): /ˌʌnbəˈliːvəbl̩/

• Audio (US):

  (file)

unbelievable (comparative more unbelievable or (rare) unbelievabler, superlative most unbelievable or (rare) unbelievablest)

2. (literally) Not to be believed.

   Synonyms: beyond belief, incredible, noncredible

   Antonyms: believable, credible

   • 1996, Colin Thompson, “Four Pigeons”, in Venus the Caterpillar and Further Wild Stories, London: Hodder Children’s Books, →ISBN, page 24:

     ‘Come on, girls,’ said Steve, ‘be honest, we won.’ / ‘Yeah,’ said Raymond, ‘we let you off because you’re girls.’ / ‘You’re unbelievable,’ said Liz. / ‘Well, if we’re unbelievable,’ said Steve, ‘then you’re unbelievabler.’

4. (figuratively) Amazing, astonishing; so surprising that one is almost, or figuratively, unable to believe.

   Synonym: incredible

   The most unbelievable thing happened to me today!

   This restaurant makes unbelievable pizza!

   • 1932 February 6, Virginia Chumley, “Visits with Virginia”, in The Chattanooga News, volume XLIV, number 189, Chattanooga, Tenn., →ISSN, →OCLC, page 11, column 6:

     Whether you want the unbelievablest sheer of chiffon . . . or the most durable of service weight . . . I’ve concluded, after a round of looking, that these stores give you a real money’s worth!

   • 1967, New Society, volume 9, London, →ISSN, →OCLC, page 680, column 1:

     In other words—join the gpo and hear the world; have fun; talk to the wildest, craziest, simply unbelievablest people.

   • 2010 March 9, Emily Lakdawalla, “Unbelievably spectacular flight through Candor Chasma”, in The Planetary Society‎, Pasadena, Calif., archived from the original on 2020-08-06:

     The unbelievablest (to coin a word) thing about this animation is the fact that it is generated in real time, like a video game!

6. Implausible or improbable.

   Synonyms: improbable, infeasible, unlikely

   Antonyms: feasible, likely, plausible, probable

   His excuse seems rather unbelievable.