n (uncountable) A common, inexpensive metal, often black in color, that rusts, is attracted by magnets, and is used in making steel.
n (uncountable|physics|chemistry|metallurgy) A metallic chemical element having atomic number 26, and symbol Fe.
n (uncountable|countable|metallurgy) Any material, not a steel, predominantly made of elemental iron.
n (countable) A tool or appliance made of metal, which is heated and then used to transfer heat to something else; most often a thick piece of metal fitted with a handle and having a flat, roughly triangular bottom, which is heated and used to press wrinkles from clothing, and now usually containing an electrical heating apparatus.
n (Cockney rhyming slang|shortened from 'iron hoof'|rhyming with 'poof'; countable|offensive) A male homosexual.
v (transitive) To pass an iron over (clothing or some other item made of cloth) in order to remove creases.