blotchn.[Cf. OE. blacche in blacchepot blacking pot, akin to black, as bleach is akin to bleak. See Black, a., or cf. Blot a spot.]1. A blot or spot, as of color or of ink; especially a large or irregular spot. Also Fig.; as, a moral blotch.()Spots and blotches . . . some red, others yellow. (Harvey.)2. (Med.) A large pustule, or a coarse eruption.()Foul scurf and blotches him defile. (Thomson.)