不足為外人道 [ㄅㄨˋ ㄗㄨˊ ㄨㄟˊ ㄨㄞˋ ㄖㄣˊ ㄉㄠˋ; bu4 zu2 wei2 wai4 ren2 dao4] no use to tell others let's keep this between ourselves (idiom) ◄ ►