a. [f. prec. + -AL: cf. F. trapézoïdal (Littré).] Having the form of a trapezoid; irregularly quadrilateral.
But sometimes misused for TRAPEZIFORM.
1795. Kirwan, Elem. Min. (ed. 2), I. 259. Oriental Garnet … presenting either 12 rhomboidal planes, or 24 trapezoidal.
1831. R. Knox, Cloquet’s Anat., 401. Each of these muscles occupies the side of the larynx; it is thin, flat, and of a trapezoidal figure.
1873. M. Collins, Squire Silchester, v. An irregular trapezoidal space, where … cattle and sheep are penned.
b. Having trapezoidal faces; trapezohedral.
1796. Kirwan, Elem. Min. (ed. 2), I. 36. When a fossil is broken into fragments, the shape of these is … sometimes cubical, rhomboidal, or pyramidal, or trapezoidal.
1805–17. R. Jameson, Char. Min. (ed. 3), 201. A Crystal is said to be … Trapezoidal, when its surface consists of twenty-four equal and similar trapeziums [i.e., trapezoids]…. Example, Trapezoidal garnet.
1822. J. Parkinson, Outl. Oryctol., 8. Its [coal’s] fragments mostly cubical or trapezoidal.
So Trapezoidiform a.
1826. Kirby & Sp., Entomol., IV. xlvi. 266. Trapezoidiform…. Whose horizontal section is trapezoid.
