iodine
Cross references: 1. element io.dine also io.din \'i--*-.di-n, -*d-*n, -*-.de-n\ n [F iode, fr. Gk ioeide-s violet colored, fr. ion violet] often attrib : a nonmetallic univalent and multivalent halogen element obtained usu. as heavy shining blackish gray crystals and used esp. in medicine, photography, and analysis