lock vs unlock

lock is a noun but unlock is not a noun.

Word	Noun	Adjective	Verb	Adverb
lock	Yes	No	Yes	No
unlock	No	No	Yes	No

lock (noun)	unlock (noun)
any wrestling hold in which some part of the opponent's body is twisted or pressured
a fastener fitted to a door or drawer to keep it firmly closed
a restraint incorporated into the ignition switch to prevent the use of a vehicle by persons who do not have the key
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
a mechanism that detonates the charge of a gun
a strand or cluster of hair

lock (verb)	unlock (verb)
become rigid or immoveable	become unlocked
fasten with a lock	open the lock of
keep engaged	set free or release
place in a place where something cannot be removed or someone cannot escape
become engaged or intermeshed with one another
hold in a locking position
build locks in order to facilitate the navigation of vessels
hold fast (in a certain state)
pass by means through a lock in a waterway