Which term refers to an irregular heartbeat?

The term that refers to an irregular heartbeat is "arrhythmia." While "dysrhythmia" can also be used to describe an irregular heart rhythm, it is more commonly regarded as a synonym for arrhythmia. Therefore, defining arrhythmia as a broader category encompassing various types of irregular heartbeats, including atrial fibrillation and various forms of tachycardia, makes it the appropriate term for the question.

Atrial fibrillation specifically describes a certain type of arrhythmia characterized by a rapid and irregular heartbeat originating in the atria of the heart. Tachycardia refers to a faster than normal heart rate but does not explicitly indicate irregularity; it simply denotes an increased heartbeat which can be regular or irregular. Hence, while "dysrhythmia" might be associated closely with irregular heartbeats, the broader and more accepted term in clinical practice is "arrhythmia."