Use the adjective revealing to describe disclosing something that was hidden, either literally or figuratively. If you ask people if they've ever cheated on a test, you may get revealing answers that tell you whether the person is honest or not.
Revealing comes from the Latin word revelare, which literally means "unveil," and that word has its roots in re-, meaning "the opposite of," and velare meaning "to cover or veil." It is little wonder that the adjective revealing is often used to describe clothing that leaves little to the imagination. If your daughter's date comes to the door in a revealing shirt with almost every button undone, you might ask him to put on a jacket or else he'll be sure to catch cold.