Definition of "rhomboidal"

Bisect it by a line drawn diagonally from the angles, and after this bisecting bring together the outlines of the figure so that it may present a rhomboidal design, reducing it by one sixth of its length and one fourth of its breadth at the (obtuse) angles.

1914, Morris Hicky Morgan, Ph.D., Ll.D., Ten Books on Architecture‎

The coupled model is global in domain and consists of GCMs of the atmosphere (spectral model with rhomboidal 30 truncation, corresponding to an approximate resolution of 3.75° longitude by 2.25° latitude, with 14 vertical levels) and ocean (1.875° longitude by 2.25° latitude, with 18 vertical levels).

2001 April 13, Sydney Levitus et al., “Anthropogenic Warming of Earth's Climate System”, in Science‎, volume 292, number 5515, pages 267–270