From Longman Dictionary of Contemporary Englishmention/note something in passingmention/note something in passingSAYif you say something in passing, you mention it while you are mainly talking about something else He did mention his brother’s wife, but only in passing. → passing
Examples from the Corpus
mention/note something in passing• He noted, in passing, that he had lasted longer than Texas Sen.• Like many more, presumably, we mention Ribblehead in passing.• In Exodus the quails were mentioned only in passing. 