What does "occlusion" mean?

Occlusion: (Med.) The transient approximation of the edges of a natural opening; imperforation. Dunglison. Occlusion of gases (Chem. & Physics), the phenomenon of absorbing gases, as exhibited by platinum, palladium, iron, or charcoal; thus, palladium absorbs, or occludes, nearly a thousand times its own volume of hydrogen, and in this case a chemical compound seems to be formed.