This adverbial use implies that something should happen without delay. For example, a fast response is expected in a fast-paced environment.
Please respond fast to my email.
I need a fast answer.
This meaning describes something that is fixed in place and cannot easily be moved. For example, an anchor is fast when holding a boat in position.
The anchor was fast in the water.
Make sure the load is fast before moving.
This meaning relates to quickly achieving a goal or turning events into action. For instance, fast-tracking a project means speeding up its progress.
She fasted through the night.
The project needs to fast-track approval.
