Crust

n. [Lat. crusta, O. Fr. crouste, N. Fr. croûte, Pr. & It. crosta, Ger. kruste, L. Ger. korste, D. korst, W. crest, from cresa, to harden by heat, to parch or scorch. See infra.] 1. The hard, external coat or covering of any thing; an exterior surface or outer shell; a concretion. I have seen the statue of an emperor quite hid under a crust of dross. Addison. And a most instant tetter barked about, Most lazar-like, with vile and loathsome crust, All my smooth body. Shak. Below the icy crust of conformity, the waters of infidelity lay dark and deep as ever. Prescott. 2. (Cookery.) (a.) The hard exterior or surface of bread, in distinction from the soft part or crumb; or a piece of bread grown dry or hard. (b.) The cover or case of a pie, in distinction from the soft contents. Though a crust of moldy bread would keep him from starving, yet they should not relieve him. Massinger.

3. (Geol.) The rocky exterior of the earth. Dana.
4. (Nat. Hist.) The shell of certain creatures, as crabs, lobsters, and the like.
5. A concreted deposit on the interior of wine bottles, being the result of the fermentation or ripening of the wine. It is composed of tartar, either red or white, and some coloring matter.