noun

• (computing, by extension) A mutex or other token restricting access to a resource.
  "[T]he application must first acquire a lock on a file or a portion of a file before reading data and modifying it."
• (firearms) The firing mechanism.
  ""I never saw such a gun in my life," replied poor Winkle, looking at the lock, as if that would do any good."
• (gambling) Synonym of Dutch book.
• (rugby) A player in the scrum behind the front row, usually the tallest members of the team.
  "Ashton only had to wait three minutes for his second try, lock Louis Deacon setting it up with a rollocking line-break, before Romania got on the scoreboard courtesy of a penalty from fly-half Marin Danut Dumbrava."

verb

• (intransitive) To become fastened in place.
  "If you put the brakes on too hard, the wheels will lock."
• (transitive) To fasten with a lock.
  "Remember to lock the door when you leave."
• (intransitive) To be capable of becoming fastened in place.
  "This door locks with a key."
• (transitive) To intertwine or dovetail.
  "with his hands locked behind his back"

noun

• (Scots law, historical) A quantity of meal, the perquisite of a mill-servant.