An article back in 2009 in Intelligent Life, entitled The Last Days of the Polymath has an interesting (if slightly uncomfortable) analogy to help distinguish dabbling in topics from depth in multiple topics.
“Nowadays people that are called polymaths are dabblers—are dabblers in many different areas,” [Carl Djerassi] says. “I aspire to be an intellectual polygamist. And I deliberately use that metaphor to provoke with its sexual allusion and to point out the real difference to me between polygamy and promiscuity."
“To me, promiscuity is a way of flitting around. Polygamy, serious polygamy, is where you have various marriages and each of them is important. And in the ideal polygamy I suspect there’s no number one wife and no number six wife. You have a deep connection with each person.”
Not sure I feel entirely comfortable using the analogy myself but the distinction certainly makes sense.