1. An abnormal growth or swelling on a plant, especially on oak trees, caused by the larva of a gall wasp or other insect.
Usage: Also called a gall.; Common in botany and entomology.
2. A hard, dark, tannin-rich gallnut from oak trees, historically used in making ink, dyes, and leather tanning.
Usage: Historical and industrial use.; Also called oak gall or nutgall.

Examples

• The oak tree was covered with gallnuts where wasps had laid their eggs.
• Medieval scribes used gallnuts to produce the iron-based ink for manuscripts.
• Gallnuts contain high concentrations of tannic acid, making them valuable for leather processing.
• The gardener noticed several gallnuts forming on the branches after the insect infestation.
• Historically, gallnuts were an important trade commodity in Europe.
• The dark, hard gallnut fell from the tree and landed on the forest floor.