From columns: Lead dancer in each column rolls back and walks by one position to arm turn the next 3/4 and spread. Trailing dancer of the lead pair follows leader and loops out and back in again to take the center wave position adjacent to dancer originally ahead of him (or her) in the column. Trailing dancer in each column steps ahead to arm turn the other trailer one quarter turn by adjacent arms and step forward to vacant center position of new parallel waves. Finishes in parallel waves.
This definition is from The Handbook of Modern Square Dancing by Jay King.
It is provided here for informational and educational purposes only.