A heart murmur is best described as an unusual sound heard during the heartbeat, caused by turbulent blood flow within the heart or great vessels. These sounds differ from normal heart sounds and can indicate underlying valvular abnormalities, septal defects, or increased flow states. Unlike arrhythmias, murmurs are audible vibrations, not rhythm disturbances. Murmurs provide crucial diagnostic clues in cardiovascular examination, guiding further evaluation. Identifying a murmur is essential for the timely management of potential structural heart diseases.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson et al., 20th Edition.