DEADBOLT
bolt, deadbolt
(noun) the part of a lock that is engaged or withdrawn with a key
Source: WordNet® 3.1
Etymology
Noun
deadbolt (plural deadbolts)
The part of the lock which is moved when the key is engaged.
A kind of lock in which the bolt (moving portion) is held in position by the cylinder rather than by a spring and so can not be retracted except by turning the cylinder.
Verb
deadbolt (third-person singular simple present deadbolts, present participle deadbolting, simple past and past participle deadbolted)
(transitive) To fasten or secure with a deadbolt.
Source: Wiktionary