noun

1. a hard, tough metal composed of iron alloyed with various small percentages of carbon and often variously with other metals, as nickel, chromium, manganese, etc., to produce hardness, resistance to rusting, etc.
2. something made of steel; specif.,
   1. Old Poet. a sword or dagger
   2. a piece of steel used with flint for making sparks
   3. a steel strip used for stiffening
   4. a roughened steel rod on which to sharpen knives
3. great strength, hardness, or toughness
4. shares of stock in steel-making companies
5. Informal steel guitar

Etymology: ME stel < OE stiele, stæli, akin to Ger stahl < IE *stak-, to stand: see stay

adjective

transitive verb

1. to cover or edge with steel
2. to make hard, tough, unfeeling, etc.