lichen

lichen n.

[植]青苔, 地衣, 苔蘚

英英解釋:名詞lichen:
1. any of several eruptive skin diseases characterized by hard thick lesions grouped together and resembling lichens growing on rocks
2. any thallophytic plant of the division Lichenes; occur as crusty patches or bushy growths on TREE trunks or rocks or bare ground etc.