lock¹ (lŏk)

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[Middle English, from Old English loc, bolt, bar.]

noun 

1. A device operated by a key, combination, or keycard and used, as on a door, for holding, closing, or securing.
2. A section of a waterway, such as a canal, closed off with gates, in which vessels in transit are raised or lowered by raising or lowering the water level of that section.
3. A mechanism in a firearm for exploding the charge.
4. An interlocking or entanglement of elements or parts.
5. 1. Sports A hold in wrestling or self-defense that is secured on a part of an opponent's body.
   2. A secure hold; control: The distributor has a lock on most of the market.
   3. A sure thing; a certainty: His promotion is a lock.

verb: locked, lock·ing, locks. 

transitive verb 

1. 1. To fasten the lock of: close and lock a drawer.
   2. To shut or make secure with or as if with locks: locked the house.
2. To confine or exclude by or as if by means of a lock: locked the dog in for the night; locked the criminal up in a cell.
3. To fix in place so that movement or escape is impossible; hold fast: The ship was locked in the ice through the winter. She felt that she had become locked into a binding agreement.
4. 1. To sight and follow (a moving target) automatically: locked the enemy fighter in the gun sights.
   2. To aim (a weapon or other device) at a moving target so as to follow it automatically: “The pilot had locked his targeting radar on the slow-moving frigate” (Ed Magnuson)
5. To engage and interlock securely so as to be immobile.
6. To clasp or link firmly; intertwine: locked arms and walked away.
7. To bind in close struggle or battle: The two dogs were locked in combat.
8. 1. To equip (a waterway) with locks.
   2. To pass (a vessel) through a lock.
9. Printing
   1. To secure (letterpress type) in a chase or press bed by tightening the quoins.
   2. To fasten (a curved plate) to the cylinder of a rotary press.
10. To invest (funds) in such a way that they cannot easily be converted into cash.
11. Computer Science
    1. To end the processing of (a magnetic tape or disk) in such a way as to deny access to its contents.
    2. To protect (a file) from changes or deletion.

intransitive verb 

1. To become fastened by or as if by means of a lock: The door locks automatically when shut.
2. To become entangled; interlock.
3. To become rigid or immobile: The mechanism tends to lock in cold weather.
4. To pass through a lock or locks in a waterway.

phrasal verbs

lock out

To withhold work from (employees) during a labor dispute.

idioms

lock horns

To become embroiled in conflict.

lock, stock, and barrel

To the greatest or most complete extent; wholly: an estate that was auctioned off lock, stock, and barrel.

under lock and key

Securely locked up.

derivatives

locḱa·ble

adjective

lock² (lŏk)

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[Middle English, from Old English locc.]

noun 

1. 1. A length or curl of hair; a tress.
   2. The hair of the head. Often used in the plural.
2. A small wisp or tuft, as of wool or cotton.