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. 4 meanings: 1. the condition or period in which some mammals, reptiles, and amphibians pass the winter in a dormant state with.... Click for more definitions. Bears are thinner following hibernation . Bats are now beginning their long winter hibernation . Research showed that some members of the mosquito species have evolved so that hibernation is triggered by a shorter day length. Definition of hibernation noun in Oxford Advanced Learner's Dictionary. Meaning , pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.