a process, available from the mid 1800's (first patented in 1837) , where iron is coated with zinc to protect it from rusting, eg galvanised roofing nails. If not done particularly well, can start to deteriorate after approx 25 years. 
Steel covered with a zinc coating to prevent rust.
galvanized, galvanised (British) Metal, or something made of metal, that is covered with a thin protective layer of zinc.