The Collaborative International Dictionary
Ferrate \Fer"rate\, n. [L. ferrum iron.] (Chem.) A salt of ferric acid.
Wiktionary
n. (context inorganic chemistry English) The anion FeO42- in which iron is in a +6 formal oxidation state.
Wikipedia
Ferrate(VI) is the inorganic anion with the chemical formula [FeO]. It is photosensitive, contributes a pale violet colour to compounds and solutions containing it and is one of the strongest water-stable oxidising species known. Although it is classified as a weak base, concentrated solutions containing ferrate(VI) are corrosive and attack the skin and are only stable at high pH.
Usage examples of "ferrate".
Pezzi di auto e di macchinari venivano trasformati in uncini, coltelli a serramanico, balestre e baliste, piccoli mangani e trabocchi per rompere i muri, clave, spadoni e mazze ferrate.