Definition of lock-in:
(n) :
Something used for fastening, which can only be opened with a key or combination.
(n) :
(computing, by extension) A mutex or other token restricting access to a resource.
(v) :
(intransitive) To become fastened in place.
(v) :
(transitive) To fasten with a lock.
(n) :
A fastening together or interlacing; a closing of one thing upon another; a state of being fixed or immovable.
(n) :
(firearms) The firing mechanism.