Yes, certainly. It's a fuzzy definition, as many things out of academia are. An urban-adjacent community would be a rural location from which you would be able to commute to work every day. For example, my brother lives in an urban-adjacent rural community and commutes to Mississauga every day. That's possible for him. I live in the middle of nowhere. It's not possible for me.
In terms of distance, that would typically be anywhere up to 100 or more kilometres. Obviously, with that being fuzzy, we know there are areas in southern Ontario that aren't strictly urban-adjacent even though their proximity might indicate otherwise. It's a combination of distance from urban and the travel patterns of the people who live there.