Any of the long, slender marine tube worms constituting the polychaete family Siboglinidae, having a beard-like plume of vascular tentacles; a pogonophoran.
Beard worms lack a mouth and gut, instead absorbing nutrients from the water and the metabolism of symbiotic bacteria. They were formerly classified as a distinct phylum Pogonophora, but more recent genetic research has identified them as aberrant polychaete annelids. Compare "pogonophoran", "vestimentiferan" noun.
1950s; earliest use found in Libbie Hyman (1888–1969), zoologist.