[li.chen] n [L, fr. Gk leichen, lichen, fr. leichein to lick] (ca. 1657) 1: any of several skin diseases characterized by a papular eruption
2: any of numerous complex thallophytic plants made up of an alga and a fungus growing in symbiotic association on a solid surface (as a rock) -- li.chened adj -- li.chen.ous adj