Look up appendage in Wiktionary, the free dictionary.
An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface appendages. In many kinds of eukaryotic cell the protrusions are known as membrane protrusions or cell appendages, such as microvilli, and cilia.