What is Iron ?
Iron is (noun) 1. a common grey metal The old gates are made of iron. (NOTE: no plural in this meaning: some iron, lumps of iron, pieces of iron) 2. a heavy object with a flat bottom, which is heated and used to make clothes smooth after washing Don’t leave the iron plugged in, it will burn the clothes. If your iron is not hot enough it won’t take the creases out. 3. a golf club with a metal head 4. in irons with iron chains tied around the ankles to prevent escape (verb) 1. to make cloth smooth, using an iron She was ironing shirts when the telephone rang. Her skirt doesn’t look as though it has been ironed. 2. to iron out to deal with a problem We had a very productive morning – all the remaining problems were ironed out.
source: Easier English, Student Dictionary Upper Intermediate Level