Source : Webster's Revised Unabridged Dictionary (1913)

Encapsulation \En*cap`su*la"tion\, n. (Physiol.)
   The act of inclosing in a capsule; the growth of a membrane
   around (any part) so as to inclose it in a capsule.

Source : WordNet®

encapsulation
     n 1: the condition of being enclosed (as in a capsule); "the
          encapsulation of tendons in membranous sheaths"
     2: the process of enclosing (as in a capsule)

Source : Free On-Line Dictionary of Computing

encapsulation
     
        1. The technique used by layered protocols in which a layer
        adds header information to the protocol data unit (PDU) from
        the layer above.  As an example, in Internet terminology, a
        packet would contain a header from the physical layer,
        followed by a header from the network layer (IP), followed by
        a header from the transport layer (TCP), followed by the
        application protocol data.
     
        2. The ability to provide users with a well-defined interface
        to a set of functions in a way which hides their internal
        workings.  In {object-oriented programming}, the technique of
        keeping together data structures and the methods (procedures)
        which act on them.
     
        (1998-09-07)