nutgall(redirected from oak apple)
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An excrescence on Quercus infectoria (family Fagaceae) and sometimes other species of Quercus (oak), caused by the deposit of the ova of a fly, Cynips gallae tinctorae; an astringent and styptic because of the tannin it contains.
A growth on certain oak trees produced by insect eggs and larvae. Gallic and tannic acids are obtained from these growths.