arrhythmic (adj.) Look up arrhythmic at Dictionary.com
1853, "without rhythm," in relation to musical sensibility, Modern Latin, from Greek arrhythmos "irregular, unrhythmical, without measure," from a- "not" (see a- (3)) + rhythmos (see rhythm). Medical arrhythmia "irregularity of pulse" is attested from 1888, from Greek noun of action from arrhythmos. Related: Arrhythmically.