Complex sentence: A stunner is a common term in professional wrestling referring to the seated three-quarter facelock jawbreaker manoeuvre, predominantly used by Stone Cold Steve Austin and named for his "Stone Cold Stunner" finisher.
Split into simpler sentences: A stunner is a common term in professional wrestling referring to the seated three-quarter facelock jawbreaker maneuver. It was then popularized by Stone Cold Steve Austin and named for his "Stone Cold Stunner" finisher.