From parallel waves: Those facing in step thru and move into the center to Swing Thru and Turn Thru. Those facing out Split Circulate or "flip" into vacated adjacent spot. Finishes in parallel waves. If started in left handed waves, dancers in the center will Left Swing Thru and Left Turn Thru to finish in parallel left handed waves.
Vince Di Caudo 1971
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.