Bromide is the reduced form of bromine. It is an ion. It exists when another element, such as sodium, gives away electrons to bromine, turning it into bromide. The aluminium turns into an aluminum ion, and both ions bond to form sodium bromide, a chemical compound. Bromides are normally colorless and nontoxic.
Bromide can also refer to an overused saying or idiom, such as "quick as a mouse" and "big as an elephant". In writing it is recommended to use fresh expressions and not over used ones.