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flip
flip sth on
flip sth off
按(開關(guān))；按(按鈕)；開(或關(guān))(機器等)
同義詞：flick
to flip a switch
按開關(guān)
She reached over and flipped off the light.
她伸過手去關(guān)掉了燈。
signal
信號；暗號
同義詞：sign
a danger / warning / distress etc. signal
危險、警告、遇難等信號
At an agreed signal they left the room.
收到約定的信號后,他們離開了房間。
The siren was a signal for everyone to leave the building.
警報器一響,就是要所有人離開大樓。
When I give the signal, run!
我一發(fā)信號,你就跑！
backup
增援；后援
The police had backup from the army.
警方得到了軍方的增援。
We can use him as a backup if six of the other players drops out.
如果有參賽者退出,我們可以用他作為替補。
a backup power supply
備用電源
