This is the 894th most frequent Russian word.
железной
"Железной" means "iron" (adjective), relating to iron or made of iron.
Adjective describing the quality of willpower.
У неё железной волей.
She has an iron will.
Adjective indicating the physical material of the handle.
Я открыл дверь железной ручкой.
I opened the door with an iron handle.
Adjective describing the strictness or rigor of discipline.