Merriam-Webster Collegiate Dictionary - molt

 I. verb  Etymology: alteration of Middle English mouten, from Old English -mutian to change, from Latin mutare — more at mutable  Date: 15th century  intransitive verb to shed hair, feathers, shell, horns, or an outer layer periodically  transitive verb to cast off (an outer covering) periodically; specifically to throw off (the old cuticle) — used of arthropods  • ~er noun  II. noun  Date: 1815 the act or process of ~ing; specifically ecdysis