Definition from macmillandictionary.com
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We drove as fast as we could to the hospital.
I can’t run very fast.
Can’t you work any faster?
The business has grown very fast.
This company is fast becoming a major exporter of computer software.
You need to get help fast!
We got there as fast as we could.
She held fast to the railings and refused to move.
The van was stuck fast in the mud.