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(plant pathology)
A gall resembling a nut.



a gall formed on young branches and leaves of certain species of oak and sumac. Gallnuts form at the sites where the larvae of gall wasps or aphids develop. They are spherical or somewhat elongated excrescences measuring 1.5–2 cm or more in diameter. Gallnuts contain tannins (up to 70 percent of the dry mass), which are used for tanning leather and making pharma ceuticals (for example, astringents).

References in periodicals archive ?
Gallnut extract is a beneficial natural adjunct in sun care, after-sun care and anti-aging formulations.
in order to tap into the Korean market and has also introduced three new natural actives in the past year--coffee bean extract, gallnut extract and rosemary T3 complex.
The Greek engineer pioneers an early ink derived from gallnuts (oak tree growths).