Definition of lichen
1 : any of numerous complex plantlike organisms made up of an alga or a cyanobacterium and a fungus growing in symbiotic association on a solid surface (such as on a rock or the bark of trees) ◆The main body of the lichen, known as the thallus, is formed by fungal filaments which surround the photosynthetic algal or cyanobacterial cells. The lichen is usually described as having a leaflike (foliose), crusty (crustose), or branching shrublike (fruticose) form. Lichens often play an important part in the weathering of rocks and include some that are sources of natural dyes.
2 : any of several skin diseases characterized by the eruptions of flat papules
lichenedplay \ˈlī-kənd, British also ˈli-chənd\ adjective
lichenousplay \ˈlī-kə-nəs, British also ˈli-chə-\ adjective
Recent Examples of lichen from the Web
Some of the objects, like cheezeballs, look surprisingly at home growing out of a tree, reminiscent of the nearly neon lichen that forms among forests in certain parts of the country.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lichen'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of lichen
Latin, from Greek leichēn, lichēn, from leichein to lick
First Known Use: circa 1657See Words from the same year
LICHEN Defined for English Language Learners
Definition of lichen for English Language Learners
: a type of small plant that grows on rocks and walls
LICHEN Defined for Kids
Definition of lichen for Students
: a plantlike organism made up of an alga and a fungus growing together
Medical Definition of lichen
1: any of several skin diseases characterized by the eruption of flat papules; especially : lichen planus
2: any of numerous complex plantlike organisms made up of an alga and a fungus growing in symbiotic association on a solid surface (as a rock)
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