Meaning of “clock” - Learner’s Dictionary

clock

noun [ C ] uk us /klɒk/
TIME

A1 a piece of equipment that shows you what time it is, usually in a house or on a building:

She could hear the hall clock ticking.
VEHICLE UK

a piece of equipment in a vehicle for measuring how far it has travelled:

The car has 63,000 kilometres on the clock.
around/round the clock

all day and all night:

Rescue teams are working round the clock to search for survivors of the earthquake.
race/work against the clock

to do something as fast as you can in order to finish before a particular time

→ See also alarm clock , grandfather clock , turn/put the clock back

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