n.: once in a while b, at times, by turns, now ... again ..., now ... then ..., now ... now ..., every now and again (=every once in a while), every now and then (=every once in a while), now and again (=every once in a while), now and then (=every once in a while), by catches, now and then, every now and then, off and on
adv.: then at irregular intervals, occasionally, from time to time