to and fro
alternately, back and forth, backward and forward, backwards and forwards, by turns, capriciously, changeably, desultorily, erratically, every other, hitch and hike, in and out, in rotation, in turns, inconstantly, make and break, mutatis mutandis, off and on, on and off, reciprocally, ride and tie, round and round, seesaw, shuttlewise, turn about, uncertainly, unsteadfastly, unsteadily, up and down, variably, vice versa, waveringly
to and fro
oscillation, vibration, libration, motion of a pendulum, nutation, undulation, pulsation, pulse, alternation, coming and going, ebb and flow, flux and reflux, ups and down, fluctuation, vacillation, wave, vibratiuncle, swing, beat, shake, wag, seesaw, dance, lurch, dodge, logan, loggan, rocking-stone, vibroscope, oscillating, oscillatory, undulatory, pulsatory, libratory, rectilinear, vibratory, vibratile, pendulous, to and fro
, up and down, backwards and forwards, hither and yon, seesaw, zigzag, wibble-wabble, in and out, from side to side, like buckets in a well.