Passing the winter in a sleeping or inactive condition. Bears, ground squirrels, woodchucks, and several other kinds of animals hibernate.

Link to present incidents:
Philae comet lander 'wakes up' from hibernation to resume Rosetta mission. Spacecraft makes contact with scientists for first time in seven months after losing power following touchdown on comet 67P/Churyumov-Gerasimenko. (The Guardian)