: any of a genus (Usnea of the family Usneaceae) of widely distributed lichens (such as old-man's beard) that have a grayish or yellow pendulous freely branched thallus

Examples of usnea in a Sentence

Recent Examples on the Web The usnea—also called old-man's beard—looked ethereal in the dappled afternoon sunlight. Hannah Wallace, Condé Nast Traveler, 6 Aug. 2021

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'usnea.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin, from Arabic ushna moss

First Known Use

1597, in the meaning defined above

Time Traveler
The first known use of usnea was in 1597

Dictionary Entries Near usnea

Cite this Entry

“Usnea.” Dictionary, Merriam-Webster, Accessed 2 Mar. 2024.

Medical Definition


Us·​nea ˈəs-nē-ə How to pronounce Usnea (audio)
: a genus of widely distributed lichens (family Usneaceae) including old-man's beard from which usnic acid is obtained
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