往返双程光信号
To-and-fro two way light signal
20米往返跑
20-meter shuttle run test
被遣返往内地
be sent back across the border
垂直往返式冷凝器
vertical reciprocating condenser
反射波往返时
round travelling time of reflection wave
世事往往会功亏一篑
There’s many a slip’twixt the cup and the lip