鉄 iron

If you're feeling anemic, TAKE TWO iron pills and call me in the morning.

He was digging for gold, but missed out and found only iron ore.

subway ★★★★☆
地 (area) + 下 (below) + 鉄 (iron) = 地下鉄 (subway)

bad mother fucker ★★☆☆☆
鉄 (iron) + 人 (person) = 鉄人 (bad mother fucker)

'iron man,' not as in the Sabbath song, but as in a bad mother fucker. (this is the kanji from Iron Chef)

train-spotter ★☆☆☆☆ SARC

a train-spotter, a train-obsessed nerd.