noun
or vat color
: any of a large and widely used class of water-insoluble generally fast dyes (as indigoid dyes and many anthraquinone dyes) that are formed on and in textile fibers by oxidation of a soluble reduced leuco form either prepared previously in a vat (sense 2b) or produced on the fibers by treating with a suspension or paste containing the unreduced dye and then reducing — see dye table I, solubilized vat dye