trapezoidal, a.
(træpɪˈzɔɪdəl)
[f. prec. + -al1: cf. F. trapézoïdal (Littré).]
a. Having the form of a trapezoid; irregularly quadrilateral. Sometimes used for trapeziform; this sense is standard in the U.S.
| 1796 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. 1955 Sci. Amer. Mar. 101/2 The temple has a trapezoidal central pyramid. 1973 Nature 21 Sept. 160/1 Trace brightness was modulated by a periodic trapezoidal wave⁓form. |
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 trapeˈzoidiform a.
| 1826 Kirby & Sp. Entomol. IV. xlvi. 266 Trapezoidiform... Whose horizontal section is trapezoid. |