1. by the by - Adjective
2. by the by - Phrase
by the by
Used to introduce a new topic; incidentally, by the way.
by the by (comparative more by the by, superlative most by the by)
Incidental; unplanned.
Synonyms: accidental, causeless, random; see also Thesaurus:accidental
by-the-by
Alternative spelling of by the by
by-the-by