1. A blot or spot, as of colour or of ink; especially a large or irregular spot. Also fig.; as, a moral blotch. Spots and blotches . . . Some red, others yellow. (Harvey)
2. (Science: medicine) a large pustule, or a coarse eruption. Foul scurf and blotches him defile. (Thomson)
Origin: cf. Oe. Blacche in blacchepot blacking pot, akin to black, as bleach is akin to bleak. See black, or cf. Blot a spot.