Lock definition

, from

Something used for fastening, which can only be opened with a key or combination.
- 1883, Robert Louis Stevenson, Treasure Island
  
  "Give me the key," said my mother; and though the lock was very stiff, she had turned it and thrown back the lid in a twinkling.
A mutex or other token restricting access to a resource.
- 2005, Karl Kopper, The Linux Enterprise Cluster
  
  ...the application must first acquire a lock on a file or a portion of a file before reading data and modifying it.
A segment of a canal or other waterway enclosed by gates, used for raising and lowering boats between levels.
- 1846, William Makepeace Thackeray, Notes of a Journey from Cornhill to Grand Cairo
  
  Here the canal came to a check, ending abruptly with a large lock.
The firing mechanism of a gun.
- 1837, Charles Dickens, The Pickwick Papers
  
  "I never saw such a gun in my life," replied poor Winkle, looking at the lock, as if that would do any good.
Complete control over a situation.
- 2003, Charley Rosen, The Wizard of Odds
  
  Even though he had not yet done so, Jack felt he had a lock on the game.
Something sure to be a success.
- 2004, Avery Corman, A perfect divorce
  
  Brian thinks she's a lock to get a scholarship somewhere.
A player in the scrum behind the front row, usually the tallest members of the team.

. Cognate with ( > ), . It has been theorised that the word may be related to the verb in its ancient meaning to curb.

tuft or length of hair
- 1847, Emily Brontë, Wuthering Heights
  
  If I consent to burn them, will you promise faithfully neither to send nor receive a letter again, nor a book (for I perceive you have sent him books), nor locks of hair, nor rings, nor playthings?

To become fastened in place

If you put the brakes on too hard, the wheels will lock.
To fasten with a lock.

Remember to lock the door when you leave.
To freeze one's body or a part thereof in place

a pop and lock routine