n. & v.
n. 1 a the hard outer part of a loaf of bread. b a piece of this with some soft bread attached. c a hard dry scrap of bread. d esp. Austral. sl. a livelihood (what do you do for a crust?). 2 the pastry covering of a pie. 3 a hard casing of a softer thing, e.g. a harder layer over soft snow. 4 Geol. the outer portion of the earth. 5 a a coating or deposit on the surface of anything. b a hard dry formation on the skin, a scab. 6 a deposit of tartar formed in bottles of old wine. 7 a sl. impudence (you have a crust!). b a superficial hardness of manner.
v.tr. & intr. 1 cover or become covered with a crust. 2 form into a crust. crustal adj. (in sense 4 of n.).
[ ME f. OF crouste f. L crusta rind, shell ]