Once in a while' is an expression used to describe something that happens INFREQUENTLY or IRREGULARLY. The crossword solutions for this term include 'OCCASIONALLY' (12 letters), 'RARELY' (6 letters), 'HARDLY' (6 letters), 'PERIODICALLY' (12 letters), 'INFREQUENTLY' (12 letters), 'IRREGULARLY' (11 letters), 'SOMETIMES' (9 letters), 'SPORADICALLY' (12 letters), 'EVERY' (5 letters), 'SELDOM' (6 letters), 'attimes' (7 letters), 'UNOFTEN' (7 letters), 'notoften' (8 letters), 'offandon' (8 letters), 'nowandthen' (10 letters), 'onoccasion' (10 letters), 'nowandagain' (11 letters), 'onceortwice' (11 letters), 'INTERMITTENTLY' (14 letters), and 'everynowandthen' (15 letters). All of these words can be used to describe something that happens INFREQUENTLY or IRREGULARLY, with some words being more specific than others.