The Collaborative International Dictionary of English v.0.48:

enclosing \enclosing\ n.
   the act of surrounding something with something else, so that
   it is inside the surrounding object.

   Syn: inclosing, enclosure, envelopment, enveloping,
        inclosure.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

enclosing
    n 1: the act of enclosing something inside something else [syn:
         enclosure, enclosing, envelopment, inclosure]