1.  crustaceous(a = adj.pert) crustacean - of or belonging to the class Crustacea;
Derived form noun crustacea₁

2.  crustaceous(a = adj.pert) - being or having or resembling a hard crust or shell;

1.  Pertaining to, or of the nature of, crust or shell; having a crustlike shell. [1913 Webster]

2.  Belonging to the Crustacea; crustacean. [1913 Webster]

semi crustaceous