polyp

(noun) a small vascular growth on the surface of a mucous membrane. Synonyms: polypus.

(noun) one of two forms that coelenterates take (e.g. a hydra or coral): usually sedentary with a hollow cylindrical body usually with a ring of tentacles around the mouth. Example: "In some species of coelenterate, polyps are a phase in the life cycle that alternates with a medusoid phase."