strong arm; iron arm
Refers to a physically powerful arm or, by extension, a person with great strength or capability. Often used in compound expressions like 鉄腕アトム (Astro Boy) or 鉄腕投手 (iron-armed pitcher).
He is a pitcher known for his iron arm.
Astro Boy (literally 'Iron Arm Atom') is Osamu Tezuka's masterpiece.
He showed off his iron arm on the mound, striking out batter after batter.
Standard kanji spelling; literally 'iron arm'.
Compound of 鉄 (iron) and 腕 (arm). The exact historical derivation is uncertain, but the word is conventionally associated with the idea of an arm as strong as iron.