catechu or cutch, extract from the heartwood of Acacia catechu, a leguminous tree of the pulse family, native to India and Myanmar. Catechu is a fast brown dye used for various shades of brown and olive, including the familiar khaki, and also in tanning. White cutch is a synonym for gambier, a leaf extract of a shrub (Uncaria gambir) of the madder family, which is similarly used.