Meaning of the word lichen in English

What does lichen mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

lichen

US /ˈlaɪ.kən/
UK /ˈlaɪ.kən/

Noun

a simple slow-growing plant that typically forms a low crustlike, leaflike, or branching growth on rocks, walls, and trees

Example:
The old stone wall was covered with green and gray lichen.
Some species of lichen are very sensitive to air pollution.