Real Dictionary

ferrotype in American English
a positive photograph taken directly on a thin plate of black-enameled iron coated with a sensitized emulsion; tintype
to give a glossy finish to (a photographic print) by squeezing into contact with a highly polished surface, usually chromium-plated steel, stainless steel, or plastic
noun: a positive photograph made on a sensitized sheet of enameled iron or tin
transitive verb: to put a glossy surface on (a print) by pressing, while wet, on a metal sheet (ferrotype tin)

ferrotype in British English
noun: a photographic print produced directly in a camera by exposing a sheet of iron or tin coated with a sensitized enamel