lichen definition

  • noun:
    • A fungus, usually associated with the class Ascomycetes, that develops symbiotically with algae, causing a composite organism that characteristically types a crustlike or branching growth on rocks or tree trunks.
    • Pathology some of different skin conditions characterized by patchy eruptions of tiny, firm papules.
    • Any of numerous symbiotic organisms, becoming associations of fungi and algae; frequently discovered as white or yellowish patches on old walls, etc.
    • certainly one of a course of mobile, flowerless flowers, (technically known as Lichenes), having no difference of leaf and stem, often of scaly, broadened, frond-like forms, but sometimes erect or pendulous and variously branched. They derive their nourishment from environment, and create by way of spores. The species are very widely distributed, and form unusual places or spots, often of a greenish or yellowish color, upon rocks, woods, and differing systems, that they adhere with great tenacity. They are often improperly known as rock moss or tree moss.
    • A name given to several kinds of disease of the skin, esp. to 1 characterized by the eruption of small, conical or level, reddish pimples, which, if unchecked, will distribute and produce great and also deadly exhaustion.
    • In botany, a plant or veggie growth of the team Lichenes, normally familiar by its dried out aspect and grey, brown, greenish, or blackish color, as well as its appearance in crusts, scaly spots, or bush-like forms on trees, rails, rocks, etc.
    • In pathology, an eruption of papules, of a red or pale color, that do not reach a vesicular or pustular phase. They might be in clusters or spread, or disseminated on the area of the skin; that will be attended with itching, like in lichen ruber, or may be quite without it, as with lichen scrofulosorum.
    • any one of a few eruptive skin conditions characterized by hard thick lesions grouped collectively and resembling lichens developing on rocks
    • any thallophytic plant associated with the unit Lichenes; take place as crusty spots or bushy growths on tree trunks or rocks or bare ground etc.
  • verb-transitive:
    • To cover with lichens.
  • others:
    • To lichenize.

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