lock

noun
  1. A device used for securing a door, gate, lid, drawer, or other object to prevent access or use. noun
    She turned the key in the lock and opened the door.
    The lock on the safe was very difficult to pick.
  2. A section of a canal or river with gates at each end where the water level can be changed to raise or lower boats. noun
    The boat entered the lock and waited for the water level to rise.
    They watched as the lock filled with water, lifting the barge.
  3. A secure hold or grip, often used in wrestling or martial arts. noun
    He put his opponent in a tight lock to prevent escape.
    The wrestler used a headlock to gain control.
  4. A piece or tuft of hair. noun
    She cut off a lock of her hair and placed it in the envelope.
    A lock of his hair fell across his forehead as he worked.
  5. To fasten or secure something with a lock. verb
    Please lock the door when you leave.
    He forgot to lock the car, and it was broken into.
  6. To become fixed or immovable. verb
    The gears locked, and the machine stopped working.
    Her knees locked, and she couldn't move.
  7. To engage in a struggle or conflict. verb
    The two teams locked in a fierce battle for the championship.
    They locked horns over the proposed changes.