Hibernate/ˈhaɪbərneɪt/ Definition 1 of 2Pro Tip 1/3Seasonal Behavior Used for animals or insects that become inactive during colder months. Some species of bats hibernate to survive winter. Pro Tip 2/3Not Just Sleep 'Hibernate' implies a period of inactivity, not just a regular sleep. Toads don't just sleep in mud; they hibernate. Pro Tip 3/3Metabolic Slowdown Hibernation involves slowing down the metabolism, not just motionlessness. During hibernation, a groundhog's heart rate drops significantly.