- a person trained in library science and engaged in library service.
- a person in charge of a library, especially the chief administrative officer of a library.
- a person who is in charge of any specialized body of literature, as a collection of musical scores.
- a person in charge of or assisting in a library
n.“custodian of a library,” 1713; see library + -an. Earlier form was library-keeper (1640s), and librarian was used earlier in a sense “scribe” (1660s).