To reveal, divulge, or make (something) known; disclose.
To reveal or disclose and show the presence or true character of, especially if unintentionally or incidentally, or else if perfidiously, prejudicially, or to one's discredit.
To expose or rat out (someone).
To inadvertently reveal any secret, particularly a secret that puts one at an advantage or disadvantage.
In card playing, to accidentally reveal one's cards or hand.