| 1. | the brown, hard outer portion or surface of a loaf or slice of bread (distinguished from crumb ). |
| 2. | a slice of bread from the end of a loaf, consisting chiefly of this. |
| 3. | the pastry covering the outside of a pie or other dish. |
| 4. | a piece of stale bread. |
| 5. | any more or less hard external covering or coating: a crust of snow. |
| 6. | Geology. the outer layer of the earth, about 22 mi. (35 km) deep under the continents and 6 mi. (10 km) deep under the oceans. Compare mantle (def. 3), core 1 (def. 10). |
| 7. | a scab or eschar. |
| 8. | Slang. unabashed self-assertiveness; nerve; gall: He had a lot of crust going to the party without an invitation. |
| 9. | deposit from wine, as it ripens during aging, on the interior of bottles, consisting of tartar and coloring matter. |
| 10. | the hard outer shell or covering of an animal. |
| 11. | Australian Slang. a living or livelihood: What do you do for a crust? |
| 12. | to cover with or as with a crust; encrust. |
| 13. | to form (something) into a crust. |
| 14. | to form or contract a crust. |
| 15. | to form into a crust. |

In geology, the outermost layer of the Earth. It overlies the mantle.
Note: The crust includes the continents and the ocean bottom and is generally estimated to be about five to twenty-five miles thick.
Note: The crust is made from relatively lightweight rocks that floated to the surface when the Earth was molten early in its history.
crust
|
crust (krŭst)
n.
A hard, crisp covering or surface.
An outer layer or coating formed by the drying of a bodily exudate such as pus or blood; a scab.
| crust (krŭst) Pronunciation Key
The solid, outermost layer of the Earth, lying above the mantle. ◇ The crust that includes continents is called continental crust and is about 35.4 to 70 km (22 to 43.4 mi) thick. It consists mostly of rocks, such as granites and granodiorites, that are rich in silica and aluminum, with minor amounts of iron, magnesium, calcium, sodium, and potassium. ◇ The crust that includes ocean floors is called oceanic crust and is about 4.8 to 9.7 km (3 to 6 mi) thick. It has a similar composition to that of continental crust, but has higher concentrations of iron, magnesium, and calcium and is denser than continental crust. The predominant type of rock in oceanic crust is basalt. |