¹ lock noun

• a device that keeps something (such as a door, window, or box) from being opened and that is usually opened by using a key
• an area in a canal or river that has gates at each end which are opened and closed to control the level of the water in different sections of the canal or river as boats move through it
• a method of holding someone so that the person being held cannot move

² lock verb

• to fasten (something) with a lock
• to fasten the door, lid, etc., of (something) with a lock —often + up
• to become fastened with a lock

³ lock noun

• a small bunch of hair
• a person's hair