A proboscis /proʊˈbɒsɪs/ is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, the term is used to describe an elongated nose or snout.
First attested in English in 1609 from Latin proboscis, the latinisation of the Greek προβοσκίς (proboskis), which comes from πρό (pro) "forth, forward, before" + βόσκω (bosko), "to feed, to nourish". The plural as derived from the Greek is proboscides, but in English the plural form proboscises occurs frequently.
The most common usage is to refer to the tubular feeding and sucking organ of certain invertebrates such as insects (e.g., moths and butterflies), worms (including Acanthocephala, proboscis worms) and gastropod molluscs.
The Acanthocephala or thorny-headed worms, or spiny-headed worms are characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host.