Alternately

1. (adv.) In reciprocal succession; succeeding by turns; in alternate order.

2. (adv.) By alternation; when, in a proportion, the antecedent term is compared with antecedent, and consequent.

Thesaurus Entries

alternate, alternately, back-and-forth, backward and forward, backwards and forwards, capriciously, changeably, desultorily, erratically, hitch and hike, in and out, inconstantly, mutatis mutandis, off and on, on and off, reciprocal, reciprocally, reciprocative, ride and tie, round and round, seesaw, shuttlewise, sine wave, to and fro, to-and-fro, uncertainly, unsteadfastly, unsteadily, up and down, up-and-down, variably, vice versa, waveringly