Definition of lichen
- n. - One of a class of cellular, flowerless plants, (technically
called Lichenes), having no distinction of leaf and stem, usually of
scaly, expanded, frond-like forms, but sometimes erect or pendulous and
variously branched. They derive their nourishment from the air, and
generate by means of spores. The species are very widely distributed,
and form irregular spots or patches, usually of a greenish or yellowish
color, upon rocks, trees, and various bodies, to which they adhere with
great tenacity. They are often improperly called rock moss or tree
moss.
- n. - A name given to several varieties of skin disease, esp. to
one characterized by the eruption of small, conical or flat, reddish
pimples, which, if unchecked, tend to spread and produce great and even
fatal exhaustion.