lichen
nounUK /ˈlaɪ.kən/
US /ˈlaɪ.kən/
Lichen is a small gray or green plant-like thing that grows on rocks and trees.
The old stone wall was covered with patches of gray lichen.
OTHER MEANINGS
2. A slow-growing organism made of a fungus and an alga living together.
Scientists study lichen to learn about air quality.
3. Any of various skin conditions marked by small raised spots.
The doctor said the rash was a type of lichen.
4. A crusty or leafy growth found in cold, clean places like tundra.
Reindeer eat lichen during the long winter.