expression, ichidan verb
let slip a secret; let the cat out of the bag
Idiomatic expression meaning to inadvertently reveal a secret while talking. Abbreviation of the longer proverb 問うに落ちず語るに落ちる (one doesn't fall when asked, but falls when speaking).
See also: 問うに落ちず語るに落ちる
彼はつい語るに落ちて、サプライズパーティーのことを話してしまった。
He inadvertently let the cat out of the bag and told them about the surprise party.
語るに落ちたと気づいたときには、もう遅かった。
By the time I realized I had let the secret slip, it was too late.