The Collaborative International Dictionary of English v.0.48:
Rhomboidal \Rhom*boid"al\, a. [Cf. F. rhombo["i]dal.] Having, or approaching, the shape of a rhomboid. [1913 Webster]WordNet (r) 3.0 (2006):
rhomboidal adj 1: shaped like a rhombus or rhomboid; "rhomboidal shapes" [syn: rhomboid, rhomboidal]