Merriam-Webster Collegiate Dictionary - occlusion

 noun  Etymology: Latin occludere  Date: circa 1645  1. the act of occluding ; the state of being occluded: as  a. the complete obstruction of the breath passage in the articulation of a speech sound  b. the bringing of the opposing surfaces of the teeth of the two jaws into contact; also the relation between the surfaces when in contact  c. the inclusion or sorption of gas trapped during solidification of a material  2. the front formed by a cold front overtaking a warm front and lifting the warm air above the earth's surface