Source : Webster's Revised Unabridged Dictionary (1913)

Occlusion \Oc*clu"sion\, n. [See {Occlude}.]
   1. The act of occluding, or the state of being occluded.

            Constriction and occlusion of the orifice. --Howell.

   2. (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.