Synonyms for Unlikely:

adj.

improbable (adjective)
doubtful, dubitable, farfetched, implausible, improbable, incredible.
not probable (adjective)
absurd, doubtful, dubious, implausible, improbable, inconceivable, incredible, questionable, remote, unbelievable, unconvincing, unheard-of, untoward, out of the ordinary.
unheard-of (adjective)
unheard-of.

adv.

improbably (adverb)
doubtfully, implausibly, improbably, incredibly.

adv

improbably (adverb)
doubtfully, implausibly, improbably, incredibly.

n.

absurd, dubious, exotic, extraordinary, inconceivable, notable, odd, offbeat, questionable, remarkable, special, surprising, unheard-of, unique, untoward, unusual, out of the ordinary. alleged, allegedly, anecdotal, apparently, credible, likely, probable, seemingly, speculative, unfounded, unpromising, unpropitious, unsubstantiated. balanced, cohesive, combined, complementary, eclectic, graded, heterogeneous, integrated, jumbled, miscellaneous, Unapt. dim, long odds, I don't suppose, there is no question of something, you'll be lucky. unlikely (noun)
farfetched, implausible, improbable, last, outside, remote, supposed, unbelievable, unconvincing.

Other synonyms:

inconceivable, Unapt. dim. questionable. discouraging
unpromising.
Other relevant words:
absurd, alleged, allegedly, anecdotal, apparently, balanced, cohesive, combined, complementary, dim, dubious, eclectic, exotic, extraordinary, graded, heterogeneous, inconceivable, integrated, jumbled, last, likely, miscellaneous, notable, odd, offbeat, outside, probable, questionable, remarkable, remote, seemingly, special, speculative, supposed, surprising, unbelievable, unconvincing, unfounded, unheard-of, unique, unpromising, unpropitious, unsubstantiated, untoward, unusual, Unapt.

Usage examples for unlikely

  1. At last she concluded that, since he was in such strict hiding, Dudleigh Manor itself would not be an unlikely place in which to find him. – The Living Link by James De Mille
  2. I call that a bit of religion breaking out in an unlikely place. – Your Boys by Gipsy Smith
  3. It is unlikely that the attempt will be repeated at present. – Bonnie Prince Charlie A Tale of Fontenoy and Culloden by G. A. Henty