What is the meaning of Crust?

A more solid, dense or hard layer on a surface or boundary.

The external, hardened layer of certain foodstuffs, including most types of bread, fried meat, etc.

An outer layer composed of pastry

The bread-like base of a pizza.

A slice of bread cut from the end of a loaf; the heel.

The outermost layer of the lithosphere of the Earth.

The outermost layer of any terrestrial planet.

The shell of crabs, lobsters, etc.

A living.

Nerve, gall.

The head.

Ellipsis of crust punk (a subgenre of punk music)

To cover with a crust.

To form a crust.

Source: wiktionary.org