an instrument for measuring and recording time, esp. by mechanical means, usually with hands or changing numbers to indicate the hour and minute: not designed to be worn or carried about.
(initial capital letter) Astronomy. the constellation Horologium.
6.
Computers. the circuit in a digital computer that provides a common reference train of electronic pulses for all other circuits.
–verb (used with object)
7.
to time, test, or determine by means of a clock or watch: The racehorse was clocked at two minutes thirty seconds.
8.
Slang. to strike sharply or heavily: Somebody clocked him on the face.
—Verb phrases
9.
clock in, to begin work, esp. by punching a time clock: She clocked in at 9 on the dot.
10.
clock out, to end work, esp. by punching a time clock: He clocked out early yesterday.
—Idioms
11.
around the clock,
a.
during all 24 hours; ceaselessly.
b.
without stopping for rest; tirelessly: working around the clock to stem the epidemic.
12.
clean (someone's) clock, to defeat; vanquish.
13.
kill the clock, Sports. to use up as much game time as possible when one is winning, as to protect a lead in basketball, ice hockey, or football. Also, run out the clock.
14.
stop the clock, to postpone an official or legal deadline by ceasing to count the hours that elapse, as when a new union contract must be agreed upon before an old contract runs out.
An instrument other than a watch for measuring or indicating time, especially a mechanical or electronic device having a numbered dial and moving hands or a digital display.
A time clock.
A source of regularly occurring pulses used to measure the passage of time, as in a computer.
Any of various devices that indicate measurement, such as a speedometer or a taximeter.
A biological clock.
Botany The downy flower head of a dandelion that has gone to seed.
v.
clocked, clock·ing, clocks
v.
tr.
To time, as with a stopwatch: clock a runner.
To register or record with a mechanical device: clocked the winds at 60 miles per hour.
v.
intr. To record working hours with a time clock: clocks in at 8 A.M. and out at 4 P.M.
[Middle English clokke, from Old North French cloque, bell, or from Middle Dutch clocke, bell, clock, both from Medieval Latin clocca, of imitative origin.] clock'er n.
[klok] 
) Astronomy. the constellation Horologium.