Similative and figurative uses, in which steel is taken as the type of hardness.

As a type of anything hard or unyielding.

As a substance of extreme hardness; = adamant, n. Obsolete.

Taken as a type of hardness, imperishableness, insensibility, etc.

A stake or column of timber regarded as a type of something inanimate, unresponsive, stupid, etc. Cf. also as deaf as a post at deaf, adj. 1d; also…

figurative and in figurative contexts, esp. with reference to strength, hardness, or inflexibility. Cf. iron, adj. 3, 4.

figurative. As a type of something hard, inflexible, durable, or smooth.

Used in comparisons or similes, with allusion to the toughness or hardness of a pine knot.

Taken as the type of something hard, dry, or dull.