A publication issued in a series of parts or instalments, esp. a periodical; (also) a novel, story, etc., published in this way, either on its…

spec. Each of the portions of a book issued at intervals in paper covers with a view to being subsequently bound together. Cf. part-work, n. 2.

The writing or publication of a story, drama, etc., in serial form; serialization (see serialization, n. 2.). Now rare.

A book or periodical published in parts. Frequently attributive.