1. Beyond belief or understanding
   - incredible 
2. Having a probability too low to inspire belief
   - improbable, unconvincing, unlikely

See also: astounding, believability, credibility, credibleness, dumbfounding, dumfounding, fabulous, flimsy, implausible, improbable, incredulous, marvellous [Brit, Cdn], marvelous [US], tall, unbelievably, unconvincing, undreamed, undreamed of, undreamt, undreamt of, unimagined, unthinkable

Encyclopedia: Unbelievable

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