arrhythmic
1. [ adjective ] without regard for rhythm
Synonyms: arrhythmical
Related terms: unrhythmical
2. [ adjective ] not having a steady rhythm
Synonyms: jerky jerking unsteady
Examples:

"an arrhythmic heartbeat"

Related terms: irregular
Similar spelling:   arrhythmical
  arrhythmia
  arithmetic
  arithmetical
  arithmetician