a device for securing a door, gate, lid, drawer, or the like in position when closed, consisting of a bolt or system of bolts propelled and withdrawn by a mechanism operated by a key, dial, etc.

a contrivance for fastening or securing something.

(in a firearm)

the mechanism that explodes the charge; gunlock.

safety ( def. 4 ) .

any device or part for stopping temporarily the motion of a mechanism.

an enclosed chamber in a canal, dam, etc., with gates at each end, for raising or lowering vessels from one level to another by admitting or releasing water.

an air lock or decompression chamber.

complete and unchallenged control; an unbreakable hold

The congresswoman has a lock on the senatorial nomination.

Slang . someone or something certain of success; sure thing

He's a lock to win the championship.

Wrestling . any of various holds, esp. a hold secured on the arm, leg, or head

leg lock.

Horology . (in an escapement) the overlap between a tooth of an escape wheel and the surface of the pallet locking it.

Metalworking . a projection or recession in the mating face of a forging die.

to fasten or secure (a door, window, building, etc.) by the operation of a lock or locks.

to shut in a place fastened by a lock or locks, as for security or restraint.

to make fast or immovable by or as if by a lock

He locked the steering wheel on his car.

to make fast or immovable, as by engaging parts

to lock the wheels of a wagon.

to join or unite firmly by interlinking or intertwining

to lock arms.

to hold fast in an embrace

She was locked in his arms.

to move (a ship) by means of a lock or locks, as in a canal (often fol. by through, in, out, down, or up ).

to furnish with locks, as a canal.

to become locked

This door locks with a key.

to become fastened, fixed, or interlocked

gears that lock into place.

to go or pass by means of a lock or locks, as a vessel.

to construct locks in waterways. ?

lock in,

to commit unalterably

to lock in the nomination of the party's candidates.

(of an investor) to be unable or unwilling to sell or shift securities.

lock off, to enclose (a waterway) with a lock.

lock on, to track or follow a target or object automatically by radar or other electronic means.

lock out,

to keep out by or as if by a lock.

to subject (employees) to a lockout.

lock up,

to imprison for a crime.

Printing . to make (type) immovable in a chase by securing the quoins.

to fasten or secure with a lock or locks.

to lock the doors of a house, automobile, etc.

to fasten or fix firmly, as by engaging parts. ?

lock horns

to come into conflict; clash

to lock horns with a political opponent.

lock, stock, and barrel, completely; entirely; including every part, item, or facet

no matter how small or insignificant

We bought the whole business, lock, stock, and barrel.

under lock and key

securely locked up

The documents were under lock and key.