NOUN (3)

1. the torpid or resting state in which some animals pass the winter;

2. cessation from or slowing of activity during the winter; especially slowing of metabolism in some animals;

3. the act of retiring into inactivity;
- Example: "he emerged from his hibernation to make his first appearance in several years"

The Collaborative International Dictionary of English v.0.48:

Hibernation \Hi`ber*na"tion\, n. [Cf. F. hibernation.]
   The act or state of hibernating. --Evelyn.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hibernation
    n 1: the torpid or resting state in which some animals pass the
         winter
    2: cessation from or slowing of activity during the winter;
       especially slowing of metabolism in some animals
    3: the act of retiring into inactivity; "he emerged from his
       hibernation to make his first appearance in several years"