■ noun
1》 the tough outer part of a loaf of bread.
↘a hard, dry scrap of bread.
2》 a hardened layer or coating on something soft.
↘a layer of pastry covering a pie.
3》 the outermost layer of rock of which a planet consists, especially the part of the earth above the mantle.
4》 a deposit of tartrates and other substances formed in wine aged in the bottle, especially port.
5》 Brit. informal a living or livelihood: earning a ~.
■ verb [often as adjective ~ed ] form into or cover with a ~: ~ed port.
Derivatives
~al adjective ( Geology ).
Origin
ME: from OFr. crouste , from L. ~a 'rind, shell, ~'.