a fastener fitted to a door or drawer to keep it firmly closed
"I had to replace the broken lock on my front door because it wouldn't stay shut anymore."
a mechanism that detonates the charge of a gun
"The mechanic warned him never to touch the lock on the antique cannon, as it could accidentally detonate the remaining charge."
enclosure consisting of a section of canal that can be closed to control the water level; used to raise or lower vessels that pass through it
"The barge captain waited patiently as they filled the lock to lift his cargo up the river."
a restraint incorporated into the ignition switch to prevent the use of a vehicle by persons who do not have the key
"I had to leave my car unlocked at the party, so a stranger was able to drive away without even having my keys."
any wrestling hold in which some part of the opponent's body is twisted or pressured
"The referee stopped the match immediately after the wrestler escaped a painful shoulder lock that had been twisting his arm for over thirty seconds."
Something used for fastening, which can only be opened with a key or combination.
"She carefully trimmed the loose lock from her daughter's forehead to keep it out of her eyes during the game."
A tuft or length of hair, wool etc.
In plain English: A lock is a device that keeps something safe by preventing it from being opened without the right key or code.
"I need to carry my keys and lock to open the front door."
Usage: Use "lock" to refer to a single, distinct strand or thick clump of hair or wool that hangs separately from the rest. Do not use it for a fastening device unless specifically describing a piece of jewelry shaped like a lock.
become rigid or immoveable
"The therapist noticed that the patient's knees tended to lock in this exercise"
pass by means through a lock in a waterway
"The barge crew waited patiently as their vessel slowly passed through the massive lock to reach the higher river level."
build locks in order to facilitate the navigation of vessels
"The construction company plans to lock the river channel to allow larger cargo ships to bypass the dam during peak shipping season."
To become fastened in place.
"The heavy door slammed shut and seemed to lock tight against the wind, refusing to budge even when I pushed hard."
In plain English: To lock something is to fasten it so that nothing can get in or out without a key.
"Please lock the door when you leave the house."
Usage: Use "lock" to describe something that has become securely fastened by itself or through its own mechanism, such as a door that won't open because it is jammed shut. Do not use it for the act of inserting a key; instead, say you are "locking" the door when you actively secure it.
A surname.
"The Lock family has owned the bakery on Main Street for three generations."
The word "lock" comes from Old English loc, which originally meant a hole or opening. It traveled into modern English with the same meaning of an opening or fastening device.