Meaning of “fast” - Learner’s Dictionary

fast

adverb us uk /fɑːst/
Extra Examples
Isabel's heart was beating fast.We're not going to get there in time, however fast we drive.She was walking so fast I couldn't keep up with her.Prices have been rising very fast and wages haven't kept up.He can run very fast.
QUICKLY

A2 moving or happening quickly:

We ran as fast as we could.
You'll have to act fast.
fast asleep
FIRMLY

in a firm or tight way:

He tried to get away, but she held him fast.
→ See also thick and fast

(Definition of “fast adverb” from the Cambridge Learner’s Dictionary © Cambridge University Press)