A "Q wave" is a specific part of an electrocardiogram (ECG or EKG) that represents the initial negative deflection in the heart's electrical activity. It occurs during the depolarization of the ventricles, which are the heart's lower chambers. Q waves can indicate the presence of heart conditions, particularly if they are abnormally deep or wide. In a normal ECG, Q waves are typically small and may not be present in all leads. However, significant Q waves can suggest a previous myocardial infarction or heart attack, as they may indicate damage to the heart muscle.