definition:ar·rhyth·mic // (-rmk) adj. Lacking rhythm or regularity of rhythm: “a slight arrhythmic imperfection when the car idles” (Garrison Keillor).
thesaurus:ar·rhythmi·cal·ly adv. arrhythmic adj. – lacking a steady rhythm; “an arrhythmic heartbeat” – subject to change or variation; “her unsteady walk”; “his hand was unsteady as he poured the wine”; “an unsteady voice” – without regard for rhythm – not rhythmic; irregular in beat or accent