by the way

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• phrase conjunctive, speech act, idiomatic Incidentally; a parenthetical statement not timely, central, or crucial to the topic at hand; foregone, passed by, something that has already happened.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adverb introducing a different topic; in point of fact