nutgall
/ˈnʌtˌɡɔl/
noun
- A hard, round growth that forms on oak trees or other plants, often caused by insects; used historically to make ink and dye.
- The artist ground up nutgall to make a rich black ink for his drawings.
- Children collected nutgalls from the oak tree to use in a science project.
- In medieval times, scribes used nutgall ink to write manuscripts.