creosote, volatile, heavy, oily liquid obtained by the distillation of coal tar or wood tar. Creosote derived from beechwood tar has been used medicinally as an antiseptic and in the treatment of chronic bronchitis. Creosote obtained from coal tar is poisonous. It is used chiefly as a preservative for wood, e.g., in fence posts, railroad ties, and telephone poles, in which it provides protection against fungi, shipworms, and termites, and is also used as a pesticide and to treat psoriasis. Creosote is considered to be highly toxic and a likely carcinogen. It can leach out into the surrounding soil and groundwater, and the fumes exuded will kill young plants in close proximity.

Either of two entirely different substances, distilled from coal tar or wood tar. Coal-tar creosote is a complex mixture of organic compounds, largely hydrocarbons. It is a cheap water-insoluble wood preservative used for railroad ties, telephone poles, and marine pier pilings and as a disinfectant, fungicide, and biocide. Wood-tar creosote consists mainly of phenols and related compounds and was once widely used for pharmaceutical purposes.

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