1 Medicine the blockage or closing of a blood vessel or hollow organ.
2 [count noun] Meteorology a process by which the cold front of a rotating low-pressure system catches up the warm front, so that the warm air between them is forced upwards off the earth’s surface between wedges of cold air.
an occluded front.
3 Dentistry the position of the teeth when the jaws are closed.
mid 17th century: from Latin occlus- 'shut up' (from the verb occludere) + -ion
occlusion in other Oxford dictionaries
Definition of occlusion in the US English dictionary