be off
To go away quickly (as a command, also be off with you)
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Main Entry: ↑off
* * *
he was anxious to be off
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be off
I must be off [=I must leave now] if I want to make the next bus.
And the runners are off. [=the runners have started running]
They're off and running!
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Main Entry: ↑off
Useful english dictionary. 2012.