From eight chain thru formation: Those designated to By Pass do a Pass Thru as the others Pass Thru and U-Turn back. (i.e., Centers By Pass -- All Pass Thru, but those now in the center -- the former outsides -- do a U-turn back).
Holman Hudspeth 1968
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.