Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun \ˈläk\

Definition of lock

  1. 1 a :  a tuft, tress, or ringlet of hair b plural :  the hair of the head

  2. 2 :  a cohering bunch (as of wool, cotton, or flax) :  tuft

  3. 3 plural :  dreadlock 2

Origin of lock

Middle English lok, from Old English locc; akin to Old High German loc lock, Greek lygos withe, Latin luxus dislocated

First Known Use: before 12th century




Definition of lock

  1. 1 a :  a fastening (as for a door) operated by a key or a combination b :  the mechanism for exploding the charge or cartridge of a firearm

  2. 2 a :  an enclosure (as in a canal) with gates at each end used in raising or lowering boats as they pass from level to level b :  air lock

  3. 3 a :  a locking or fastening together b :  an intricate mass of objects impeding each other (as in a traffic jam) c :  a hold in wrestling secured on one part of the body; broadly :  a controlling hold <his paper … had a lock on a large part of the state — John Corry>

  4. 4 :  one that is assured of success or favorable outcome

Origin of lock

Middle English lok, from Old English loc; akin to Old High German loh enclosure and perhaps to Old English locc lock of hair

First Known Use: before 12th century

Other Hardware Terms




Simple Definition of lock

  • : to fasten (something) with a lock

  • : to fasten the door, lid, etc., of (something) with a lock

  • : to become fastened with a lock

Full Definition of lock

  1. transitive verb
  2. 1 a :  to fasten the lock of b :  to make fast with or as if with a lock <lock up the house>

  3. 2 a :  to fasten in or out or to make secure or inaccessible by or as if by means of locks <locked himself away from the curious world> b :  to fix in a particular situation or method of operation <a team firmly locked in last place>

  4. 3 a :  to make fast, motionless, or inflexible especially by the interlacing or interlocking of parts <lock wheels> <lock a knee> b :  to hold in a close embrace c :  to grapple in combat; also :  to bind closely <administration and students were locked in conflict>

  5. 4 :  to invest (capital) without assurance of easy convertibility into money

  6. 5 :  to move or permit to pass (as a ship) by raising or lowering in a lock

  7. intransitive verb
  8. 1 a :  to become locked b :  to be capable of being locked

  9. 2 :  interlace, interlock

  10. 3 :  to go or pass by means of a lock (as in a canal)

lock·able play \ˈlä-kə-bəl\ adjective
lock horns
  1. :  to come into conflict

lock on or lock onto
  1. :  to acquire (as a target or signal) automatically using a sensor (as radar)

Examples of lock

  1. They locked the door when they left and unlocked it when they returned.

  2. She locked the bicycle to the railing with a chain.

  3. He forgot to lock the car.

  4. The car locks automatically when you start the engine.

  5. The wheels locked and the car skidded off the road.

  6. They were locked in each other's arms.

  7. She locked her hands around the steering wheel.

  8. The file is locked for editing.

14th Century

First Known Use of lock

14th century

Seen and Heard

What made you want to look up lock? Please tell us where you read or heard it (including the quote, if possible).


February 14, 2016

to hug and kiss another person

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


How much does a batman (the Turkish unit of measurement) weigh?

196.5 pounds 2.2 pounds 16.96 pounds 100 pounds
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.


Test Your Knowledge - and learn some interesting things along the way.