Wheeze is a whistling noise that occurs during breathing. It is caused by turbulent or obstructed airflow and has many different causes.
The cause most people associate with wheeze is asthma, however there are different types of wheeze which are associated with different conditions. If you experience wheeze, especially with another sympotm such as breathlessness, this should be investigated.
The Patient.co.uk website has further information on wheeze and its causes.