alternate, alternately, beating, by turns, circling, cyclic, epochal, even, in rotation, in turns, intermittent, isochronal, make and break, measured, metronomic, off and on, oscillatory, periodical, pulsing, reciprocal, reciprocally, recurrent, recurring, rhythmic, rotary, round and round, seasonal, serial, steady, to and fro, turn about, undulant, undulatory, up and down, wavelike, wheeling