INCONCEIVABLE

impossible, inconceivable, out of the question, unimaginable

(adjective) totally unlikely

Source: WordNet® 3.1

Etymology

Adjective

inconceivable (comparative more inconceivable, superlative most inconceivable)

Unable to be conceived or imagined; unbelievable.

Antonyms

• conceivable

Source: Wiktionary

In`con*ceiv"a*ble, a. Etym: [Pref. in- not + conceivable: cf. F. inconcevable.]

Definition: Not conceivable; incapable of being conceived by the mind; not explicable by the human intellect, or by any known principles or agencies; incomprehensible; as, it is inconceivable to us how the will acts in producing muscular motion. It is inconceivable to me that a spiritual substance should represent an extended figure. Locke.

– In`con*ceiv"a*ble*ness, n.

– In`con*ceiv"a*bly, adv. The inconceivableness of a quality existing without any subject to possess it. A. Tucker.

Source: Webster’s Unabridged Dictionary 1913 Edition