A toxic or harmful substance.
Mufsid refers to substances that are dangerous or harmful to the body if consumed in large amounts, even if they don’t make a person drunk. For example, chemicals with very high alcohol levels or toxic additives. Individuals will be seriously harmed by the substance before any obvious drunkenness occurs. These are ḥarām (forbidden) to consume because they are poisonous or damaging to health. Other synthetic alcohols are considered mufsid e.g. industrial alcohols, cleaning solvents, or methanol-based products.