Does it mean someone who is highly proficient in the jazz tradition (Behop and hard bop) and in 1960s and beyond avant garde jazz, and who integrates the two traditions into a single style?
If so, my own favorites among saxophonists fitting this description are George Adams, Roland Kirk, Pharoah Sanders, Billy Harper, David Murray, and Eric Dolphy.
On piano, my favorite inside/outside players are Jaki Byard and Don Pullen.