Hibernation is a type of deep sleep some animals (like bears) go into during winter. Hibernation is like a long nap.
Have you ever wanted to skip from fall to spring? Some animals do just that by hibernating, which is a sleep-like state during which their metabolism slows and they conserve energy. Animals who hibernate do nothing: hibernation is a time of rest and inactivity, almost like a coma. People also use this word for other types of inactivity. For example, you could talk about the hibernation of an athlete who has taken a year off from competition.