Adjective
nonconvex (not comparable)
Not convex.
Aside from a rectangular box, orthogonal polyhedra are nonconvex. Source: Internet
Vertex arrangement The cuboctahedron shares its edges and vertex arrangement with two nonconvex uniform polyhedra : the cubohemioctahedron (having the square faces in common) and the octahemioctahedron (having the triangular faces in common). Source: Internet
The small and great stellated dodecahedron have nonconvex regular pentagram faces. Source: Internet