Definition of crust

• n. - The hard external coat or covering of anything; the hard exterior surface or outer shell; an incrustation; as, a crust of snow.
• n. - The hard exterior or surface of bread, in distinction from the soft part or crumb; or a piece of bread grown dry or hard.
• n. - The cover or case of a pie, in distinction from the soft contents.
• n. - The dough, or mass of doughy paste, cooked with a potpie; -- also called dumpling.
• n. - The exterior portion of the earth, formerly universally supposed to inclose a molten interior.
• n. - The shell of crabs, lobsters, etc.
• n. - A hard mass, made up of dried secretions blood, or pus, occurring upon the surface of the body.
• n. - An incrustation on the interior of wine bottles, the result of the ripening of the wine; a deposit of tartar, etc. See Beeswing.
• n. - To cover with a crust; to cover or line with an incrustation; to incrust.
• v. i. - To gather or contract into a hard crust; to become incrusted.