NOUN (1)

1. silky envelope spun by the larvae of many insects to protect pupas and by spiders to protect eggs;


VERB (2)

1. retreat as if into a cocoon, as from an unfriendly environment;
- Example: "Families cocoon around the T.V. set most evenings"
- Example: "She loves to stay at home and cocoon"

2. wrap in or as if in a cocoon, as for protection;

The Collaborative International Dictionary of English v.0.48:

Cocoon \Co*coon"\, n. [F. cocon, dim. of coque shell of egge and
   insects, fr. L. concha mussel shell. See Conch.]
   1. An oblong case in which the silkworm lies in its chrysalis
      state. It is formed of threads of silk spun by the worm
      just before leaving the larval state. From these the silk
      of commerce is prepared.
      [1913 Webster]

   2. (Zool.)
      (a) The case constructed by any insect to contain its
          larva or pupa.
      (b) The case of silk made by spiders to protect their
          eggs.
      (c) The egg cases of mucus, etc., made by leeches and
          other worms.
          [1913 Webster]

WordNet (r) 3.0 (2006):

cocoon
    n 1: silky envelope spun by the larvae of many insects to
         protect pupas and by spiders to protect eggs
    v 1: retreat as if into a cocoon, as from an unfriendly
         environment; "Families cocoon around the T.V. set most
         evenings"; "She loves to stay at home and cocoon"
    2: wrap in or as if in a cocoon, as for protection