clock in

WordReference Random House Learner's Dictionary of American English © 2025

clock¹ /klɑk/   n. [countable]

1. Time a relatively large instrument for telling time.
2. time clock.
3. a meter for measuring and recording speed, etc.:
   The skier is racing against the clock.
4. Biology biological clock.

v. 

5. to time, test, or determine by means of a clock or watch:
   [~ + object] The racehorse was clocked at two minutes thirty seconds.
6. clock in (or out), [no object] to begin (or end) the day's work, esp. by punching a time clock:
   What time did you clock in today?

Idioms

7. Idioms around the clock, [uncountable]
   • for the entire 24-hour day without pause:
     The factory shifts worked around the clock.
   • without stopping for rest;
     tirelessly:
     working at this project around the clock.

WordReference Random House Unabridged Dictionary of American English © 2025

clock¹  (klok), n. 

1. Time 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.
2. See time clock. 
3. a meter or other device, as a speedometer or taximeter, for measuring and recording speed, distance covered, or other quantitative functioning.
4. Biology See biological clock. 
5. (cap.) [Astron.] the constellation Horologium.
6. Computing the circuit in a digital computer that provides a common reference train of electronic pulses for all other circuits.
7. Idioms around the clock:
   • during all 24 hours;
     ceaselessly.
   • without stopping for rest;
     tirelessly:
     working around the clock to stem the epidemic.
8. Idioms clean (someone's) clock, to defeat;
   vanquish.
9. Sport kill the clock, 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. 
10. Idioms 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.

v.t. 

11. to time, test, or determine by means of a clock or watch:
    The racehorse was clocked at two minutes thirty seconds.
12. Slang Terms to strike sharply or heavily:
    Somebody clocked him on the face.

v.i. 

13. clock in, to begin work, esp. by punching a time clock:
    She clocked in at 9 on the dot.
14. clock out, to end work, esp. by punching a time clock:
    He clocked out early yesterday.

• Middle Dutch clocke bell, clock; akin to Old English clucge, Old High German glocka (German Glocke), Old Irish clocc bell; compare cloak
• Middle English clok(ke) 1350–1400

clock²  (klok), n. 

1. a short embroidered or woven ornament on each side or on the outer side of a sock or stocking, extending from the ankle upward.

v.t. 

2. to embroider with such an ornament.

• origin, originally uncertain 1520–30

Collins Concise English Dictionary © HarperCollins Publishers::

clock on, clock in verb

1. (intr, adverb) to arrive at work, esp when it involves registering the time of arrival on a card