"To expand the definition" means to broaden or increase the scope or understanding of something. It involves including more elements or aspects within a particular concept or category. Full definition
The effect of that teaching, once we accepted it, was to expand the reach of the moral sentiments by expanding the definition of who is truly human. (firstthings.com)
Off the mat, perhaps you can also grow by expanding your definition of yourself to encompass a broader range of possibility. (yogajournal.com)
Videos should be examined critically and are intended to engage students in expanding definitions of family and family engagement. (ucea.org)