The term caustic substance refers to a range of substances that are corrosive and can cause chemical burns. The most common caustic substances are LYE (3 letters), LIME (4 letters), ACID (4 letters) and lyes (4 letters). LYE is an alkaline solution made from ashes, LIME is a calcium-based compound, ACID is a sour-tasting liquid, and lyes are a type of soap made from LYE. All of these substances are highly corrosive and can cause severe burns if not handled properly.