A parenthetical remark or section is put into something written or spoken but is not essential to it. Fox was making a long parenthetical remark about his travels on the border of the country. + parenthetically par·en·the·ti·cal·ly Well, parenthetically, I was trying to quit smoking at the time And what, we may ask parenthetically, does it mean?. said or written while you are talking or writing about something else in order to explain something or add information