机不可失 jībùkěshī opportunity Origin Definitions Defs Strokes Stroke Words Sentences Sents 机不可失，失不再来 jībùkěshī, shībùzàilái opportunity knocks once opportunity knocks but once机不可失，时不再来 jībùkěshī, shíbùzàilái now or never Opportunity knocks but once.