- Arrhythmia: (a) + (rhythm)
- Abnormality in a physiological rhythm, especially in the activity of the brain or heart.
- Contrary to its apparent etymology, arrhythmia refers to any disturbance in the way the cardiac muscle contracts.
- Although the heart beat does become irregular in the most common arrhythmia (atrial fibrillation), some arrhythmias are counter-intuitively regular.
