1. The wormlike developmental stage or stages of an insect or helminth that are markedly different from the adult and undergo subsequent metamorphosis; a grub, maggot, or caterpillar. 2. The second stage in the life cycle of a tick; the stage that hatches from the egg and, following engorgement, molts into the nymph. 3. The young of fishes or amphibians that often differ in appearance from the adult.