Usnea

noun

1. Any of various widely distributed lichens of the genus Usnea, characterized by a pendulous, usually branched thallus, often growing on trees.
2. A small genus of gymnocarpous parmeliaceous lichens, typical of the family Usneëi.
3. A genus of lichens, most of the species of which have long, gray, pendulous, and finely branched fronds. Usnea barbata is the common bearded lichen which grows on branches of trees in northern forests.
4. A lichen of the genus Usnea.
5. widely distributed lichens usually having a greyish or yellow pendulous freely branched thallus