Crust
CRUST, noun [Latin , G.]
1. An external coat or covering of a thing, which is hard or harder than the internal substance; as the crust of bread; the crust of snow; the crust of dross; the crust of a pie.
2. A piece of crust; a waste piece of bread.
3. A shell, as the hard covering of a crab and some other animals.
4. A scab.
5. The superficial substances of the earth are, in geology, called its crust
CRUST, verb transitive
1. To cover with a hard case or coat; to spread over the surface a substance harder than the matter covered; to incrust; as, to crust a thing with clay; to crust cake with sugar; crusted with bark.
2. To cover with concretions.
CRUST, verb intransitive To gather or contract into a hard covering; to concrete or freeze, as superficial matter.