[sul.fur] also sul.phur n [ME sulphur brimstone, fr. L sulpur, sulphur, sulfur] (14c) 1: a nonmetallic element that occurs either free or combined esp. in sulfides and sulfates, is a constituent of proteins, exists in several allotropic forms including yellow orthorhombic crystals, resembles oxygen chemically but is less active and more acidic, and is used esp. in the chemical and paper industries, in rubber vulcanization, and in medicine for treating skin diseases
2: something (as scathing language) that suggests sulfur -- sul.fury or sul.phury adj usage The spelling sulfur predominates in U.S. technical usage, while both sulfur and sulphur are common in general usage. British usage tends to favor sulphur for all applications. The same pattern is seen in most of the words derived from sulfur.