The word lock came from Anglo-Saxon loca = "a secure enclosure". Currently lock has several meanings:

• A lock (device) a mechanical fastening device which may be used on a door, vehicle, or container. Commonly, it can be released by using a key or combination. See locksmithing.
• A canal lock is an enclosure in a canal or river used to raise or lower the water level for ships and boats passing through.
• A lock (software engineering) is, in computer science, a bookkeeping object associated with a piece of data used to serialize concurrent access.
• Any means of holding a setting or state, such as caps lock, satellite lock .
• Early projectile weapons using gunpowder such as muskets, smooth bore pistols and early rifles are classified by the ignition mechanism (called the lock (firearm)) used to fire the weapon. These include matchlock, wheellock, flintlock, and modern percussion types. A complete firearm often consists of lock, stock , and barrel.
• A wrestling hold, such as a head lock.
• A tuft or small bundle of hair.
• A position in rugby union, numbers 4 and 5. Locks are typically very tall to facilitate catching balls in the line-out. Famous locks include Martin Johnson and Colin Meads.