A Q wave is a part of the QRS wave complex for a beating heart.
Look at the normal EKG here
http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?
book=cardio&part=A39&rendertype=figure&id=A85
Look at the section labelled 1 ... you'll see a little dip before the tall upstanding wave. That's the Q wave.
Everybody normally gets a Q wave as a part of their heart beat ... but what is significant is when the Q wave is long or deep. The usual cause of Q wave irregularities is a previous heart attack (MI - myocardial infarction) resulting in dead heart muscle tissue or thickening of the heart muscle possibly from insufficient blood flow to the heart.
This is one you really must talk over with your doctor to determine the significance of a Q wave abnormality.
Beware that if you have had an EKG and saw the traces, and maybe even were given them for delivery to your doctor, the modern EKG machine prints out details of any abnormalities it has detected itself. These are "suggestions" to the doctor to look closely at. They aren't necessarily problems. So for example if it says Q waves, it's just telling the doctor to check the Q wave for a closer interpretation. It may not be significant for you, or it may be. This is what the doctor will determine based on other factors.
