Synonyms of the word

improbable

• adj. Not likely to be true.
• adj. Not likely to happen.

implausible

• adj. Not plausible; unlikely; dubious.

incredible

• adj. Too implausible to be credible; beyond belief; unbelievable.
• adj. Amazing; astonishing; awe-inspiring.
• adj. Marvellous; profoundly affecting; wonderful.

marvellous

• adj. (Britain) Exciting wonder or surprise; astonishing; wonderful.

marvelous

• adj. (US) Exciting wonder or surprise; astonishing; wonderful.

supposed

• v. simple past tense and past participle of suppose.
• adj. Presumed to be true, but without proof.
• adj. (with infinitive) Generally considered or expected.
• adj. (with infinitive) Having an obligation.
• adj. (with infinitive) Intended.

tall

• adj. (of a person) Having a vertical extent greater than the average. For example, somebody with a height of…
• adj. (of a building, etc.) Having its top a long way up; having a great vertical (and often greater than horizontal)…
• adj. (of a story) Hard to believe, such as a tall story or a tall tale.
• adj. (chiefly US, of a cup of coffee) A cup of coffee smaller than grande, usually 8 ounces.
• adj. (obsolete) Obsequious; obedient.
• adj. (obsolete) Seemly; suitable; fitting, becoming, comely; attractive, handsome.
• adj. (obsolete) Bold; brave; courageous; valiant.
• adj. (archaic) Fine; proper; admirable; great; excellent.

unbelievable

• adj. Not to be believed.
• adj. Incredible; so surprising it is almost unable to believe.
• adj. Implausible or improbable.

unconvincing

• adj. not convincing, plausible or believable.
• v. present participle of unconvince.

unlikely

• adj. Not likely; improbable; not to be reasonably expected.
• adj. Not holding out a prospect of success; likely to fail; unpromising.
• adv. In an improbable manner.
• n. Something or somebody considered unlikely.