[crust] n [ME, fr. L crusta; akin to OE hruse earth, Gk kryos icy cold, krystallos ice, crystal] (14c) 1 a: the hardened exterior or surface part of bread b: a piece of this or of bread grown dry or hard
2: the pastry cover of a pie
3: a hard or brittle external coat or covering: as a: a hard surface layer (as of soil or snow) b: the outer part of a planet, moon, or asteroid composed essentially of crystalline rocks c: a deposit built up on the interior surface of a wine bottle during long aging d: an encrusting deposit of dried secretions or exudate; esp: scab
4: gall, nerve -- crust vb -- crust.al adj -- crust.less adj