|krə|stāshəs adjective
Etymology: New Latin crustaceus, from Latin crusta shell, crust + -aceus -aceous — more at crust
1. : of the nature of, having, or suggesting a crust or shell
2. : crabby II 1, crusty 1a(2)
3. : belonging to the Crustacea : crustacean
4. botany
a. : having a brittle crust
b. of a lichen : having a crusty thallus adhering inseparably to rocks, bark, soil