iron man—
1. a tireless man of extraordinary strength:
- He likes to think of himself as some sort of iron man who doesn’t need sleep like the rest of us.
2. (sl.) a UK pound or a U.S. dollar:
- An ounce [of drug] should bring a street pusher about two thousand iron men.
man of iron—
1. = iron man 1:
- His muscles show him to be a man of iron, physically; and his firmness of purpose shows the same quality in his character.
2. a hard, unyielding or merciless man:
- Neither threats nor promises could move the man of iron to utter more than he was willing to reveal.
See also: Man of Steel / steel man.