alternate back and fill battledore and shuttlecock come and go ebb and flow flounder fluctuate go through phases hitch and hike oscillate pass and repass pendulate reciprocate ride and tie ring the changes seesaw shift shuffle shuttle shuttlecock stagger sway swing teeter teeter-totter to-and-fro totter turn vacillate vary waver wibble-wabble wigwag wobble zigzag