Brimstone

Easton's Bible Dictionary (1897)

An inflammable mineral substance found in quantities on the shores of the Dead Sea. The cities of the plain were destroyed by a rain of fire and brimstone (Gen. 19:24, 25). In Isa. 34:9 allusion is made to the destruction of these cities. This word figuratively denotes destruction or punishment (Job 18:15; Isa. 30:33; 34:9; Ps. 11:6; Ezek. 38:22). It is used to express the idea of excruciating torment in Rev. 14:10; 19:20; 20:10.

Smith's Bible Dictionary (1863)

Brimstone, or sulphur, is found in considerable quantities on the shores of the Dead Sea. (Genesis 19:24) It is a well-known simple mineral substance, crystalline, easily melted, very inflammable, and when burning emits a peculiar suffocating odor. It is found in great abundance near volcanoes. The soil around Sodom and Gomorrah abounded in sulphur and bitumen.

Public domain dictionaries.