A blotch is an irregular stain, spot, or mark that spreads unevenly across a surface. When you spill juice on your shirt, it might leave a purple blotch that has fuzzy, uneven edges rather than a neat circle. If you're painting and accidentally drip paint on the floor, that messy puddle is a blotch.

Blotches often appear on skin too. When someone gets nervous or embarrassed, red blotches might appear on their neck or cheeks. Some people get blotchy skin from allergies, with irregular pink or red patches scattered across their arms or face. Unlike a perfect polka dot or a straight line, a blotch has an organic, random shape, as if something spread out without any pattern or control.

The word suggests something unwanted or accidental. You wouldn't deliberately create blotches in your artwork (though some artists do use blotchy effects on purpose for texture). When something is blotched or blotchy, it's marked with these irregular spots, giving it an uneven, mottled look.