Mitral Valve: It is called prolapse. It occurs when the valve between your heart's left upper chamber (left atrium) and the left lower chamber (left ventricle) doesn't close properly. When the left ventricle contracts, the valve's leaflets bulge (prolapse) upward or back into the atrium.
Now if blood starts flowing backward in your heart due to your valves not closing properly it is called regurgitation.
Aortic Valve: Aortic valve regurgitation, also known as aortic insufficiency
or aortic incompetence, is a condition that occurs when your heart's aortic valve doesn't close tightly. In this condition, some of the blood that was just pumped out of your heart leaks back into it.
The Pulmonic and Tricuspid Valves, is called insufficiency or prolapse also when they do not close properly.
Stenosis of a valve is when narrowing of the valves occur.