a. [f. L. triquetrus three-cornered, triangular + -OUS.] Three-sided, triangular; in Nat. Hist. of triangular cross-section, three-edged, trihedral, triangularly prismatic or pyramidal.
1658. Sir T. Browne, Gard. Cyrus, ii. 40. The lithostrota or figured pavements of the ancients, which consisted not all of square stones, but were divided into triquetrous segments.
1752. J. Hill, Hist. Anim., 27. The grey wood Spider, with a triquetrous body.
1826. Kirby & Sp., Entomol., III. xxxiii. 432. Almost universally they [the mandibles of insects] incline to a triquetrous or three-sided figure.
1870. Hooker, Stud. Flora, 291. Lamium, Dead-nettle … nutlets 3-quetrous.
1872. Oliver, Elem. Bot., App. 309. Fruits ovoid, acutely triquetrous.
Hence Triquetrously adv.
1884. in Stormonth, Dict.
