impossibility; something impossible
Refers to a thing or matter that cannot be done or realized. Often used in formal or written contexts.
His proposal was said to be an impossibility.
Turning impossibilities into possibilities is the power of technology.
不可能 is the more common adjectival noun meaning 'impossible'; 不可能事 specifically refers to an impossible thing or matter.
Compound of 不可能 (fukanō, 'impossible') + 事 (ji, 'thing, matter').