Synonyms for Arrhythmic (same or very similar meaning)
WordNet sense 1 (not having a steady rhythm):
jerky, jerkingWordNet sense 2 (subject to change or variation):
unsteadyWordNet sense 3 (without regard for rhythm):
arrhythmicalWordNet sense 4 (not rhythmic; irregular in beat or accent):
unrhythmic, unrhythmicalFrom the ODE community, based on WordNetadd/edit