Occlusion is either the act of blocking something or a specific blockage. There can be occlusions blocking the street or your arteries. When dentists say occlusion, they’re talking about what your teeth look like when your mouth is closed.
An occlusion blocks anything that flows, like cars, people, water, or blood. You can say there's occlusion if a pipe is clogged. If you find out a golf ball was in the pipe, the ball was an occlusion. This word applies to things that block and the act of blocking. People have heart attacks when there's occlusion in their arteries. An overturned truck would be an occlusion on the highway. Occlusions are in the way.