keep secret; hush sth. up; keep sth. under one's hat; keep sth. dark; keep sth. under cover [under wraps]; keep the news (of sth.) from getting out; not to let anyone into a secret
不宣而战 start an undeclared war; fight without a declaration of war; open hostilities without declaring war
肺气不宣 fei qi bu xuan lung qi not diffusing; obstruction of pulmonary qi
心照不宣 both understand from their hearts what the matter is but do not choose to say so in public.; have a tacit (mutual) understanding; no need to express oneself in so many words; no need to say how grateful (i am); not necessary to say more; think it is not necessary to say more; thoroughly understand each other, without having exchanged a word of explanation; take wordless counsel