lock¹ / läk/ • n. 1. a mechanism for keeping a door, lid, etc., fastened, typically operated only by a key of a particular form: the key turned firmly in the lock. ∎  a similar device used to prevent the operation or movement of a vehicle or other machine: a bicycle lock. ∎  (in wrestling and martial arts) a hold that prevents an opponent from moving a limb. ∎  [in sing.] archaic a number of interlocked or jammed items: a street closed by a lock of carriages.2. a short confined section of a canal or other waterway in which the water level can be changed by the use of gates and sluices, used for raising and lowering vessels between two gates. ∎  an airlock.3. (a lock) inf. a person or thing that is certain to succeed; a certainty.4. archaic a mechanism for exploding the charge of a gun. • v. 1. [tr.] fasten or secure (something) with a lock: she closed and locked her desk | [as adj.] (locked) behind locked doors. ∎  (lock something up) shut and secure something, esp. a building, by fastening its doors with locks: the diplomatic personnel locked up their building and walked off | [intr.] you could lock up for me when you leave. ∎  enclose or shut in by locking or fastening a door, lid, etc.: the prisoners are locked up overnight Phil locked away the takings every night. ∎  (lock someone up/away) imprison someone. ∎  (lock something up/away) invest money in something so that it is not easily accessible: vast sums of money locked up in pension funds. ∎  (lock someone down) confine prisoners to their cells, esp. so as to gain control. ∎  [intr.] (of a door, window, box, etc.) become or be able to be secured through activation of a lock: the door will automatically lock behind you.2. make or become rigidly fixed or immovable: [tr.] he locked his hands behind her neck | [intr.] their gaze locked for several long moments. ∎  (lock someone/something in) engage or entangle in (an embrace or struggle): they were locked in a legal battle. ∎  trap or fix firmly or irrevocably. this may tend to lock in many traders with their present holdings. ∎  (lock someone/something into) cause to become caught or involved in: they were now locked into the system. ∎  (of land, hills, ice, etc.) enclose; surround: the vessel was locked in ice.3. [intr.] go through a lock on a canal: we locked through at Moore Haven.PHRASES: have a lock on inf. have an unbreakable hold on or total control over.lock horns engage in conflict.lock, stock, and barrel including everything; completely: the place is owned lock, stock, and barrel by an oil company.under lock and key securely locked up.PHRASAL VERBS: lock onto locate (a target) by radar or similar means and then track.lock someone out1. keep someone out of a room or building by locking the door.2. (of an employer) subject employees to a lockout.lock someone out of exclude someone from: those now locked out of the job market.DERIVATIVES: lock·a·ble adj.lock·less adj.lock² • n. a piece of a person's hair that coils or hangs together: she pushed back a lock of hair. ∎  (locks) chiefly poetic/lit. a person's hair: flowing locks and a long white beard. ∎  a tuft of wool or cotton. ∎  (locks) short for dreadlocks.DERIVATIVES: locked adj. his curly-locked comrades.