usnic acidPronunciation: /ˈʌznɪk/Definition of usnic acid noun [mass noun] Biochemistry a yellow crystalline compound which is present in many lichens and is used as an antibiotic. A tricyclic phenol; chemical formula: C18H16O7 Origin: mid 19th century: usnic from medieval Latin usnea (from Arabic ushnah 'moss') + -icusnic acid in other Oxford dictionaries Definition of usnic acid in the US English dictionary
