断弦
widowed; lit. broken string, cf 琴瑟[qin2 se4] qin and se, two instruments epitomizing marital harmony
断线
(of a guitar, kite etc) to have a string break; (of a tradition etc) to be discontinued; (telephone or Internet connection) disconnected; cut off
端线
end line; baseline (sports)
断线风筝
a kite with cut string (idiom); fig. gone beyond recall