Molt/məʊlt/ Definition 1 of 2Pro Tip 1/3Cyclical Renewal Molt signifies a recurring process for renewal in animals, hinting at natural cycles. Birds molt annually to renew their plumage. Pro Tip 2/3Natural Phenomenon Molt is often used to describe a natural, biological process, not an artificial one. Watching a caterpillar molt into a chrysalis is fascinating. Pro Tip 3/3Specific Creatures Not all animals molt, so it's mainly used with birds, reptiles, and arthropods. Did you know some spiders also molt?