: an abnormal outgrowth of plant tissue usually due to insect or mite parasites or fungi and sometimes forming an important source of tannin — see gall wasp illustration
Origin of GALL
Middle English galle, from Anglo-French, from Latin galla
First Known Use: 14th century
Abnormal, localized outgrowth or swelling of plant tissue caused by infection from bacteria, fungi, viruses, or nematodes, or by irritation by insects and mites. The common plant disease crown gall, characterized by the proliferation of galls on the roots and lower stems, is caused by the bacterium Agrobacterium tumefaciens.