a. Also 6–7 equilaterall, (7 æqui-). [ad. late L. æquilaterālis, f. æqui- (see EQUI-) + latus, later-is side + -AL.]
Having all the sides equal.
Equilateral arch: an arch, in which the chords of the sides form with the base an equilateral triangle. Equilateral hyperbola, one whose axes are equal. Equilateral shell, one in which a transverse line drawn through the apex of the umbo divides the valve into two equal and symmetrical parts.
1570. Billingsley, Euclid, I. i. 10. How to describe an equilaterall triangle redily and mechanically.
1634. Sir T. Herbert, Trav., 112. The Sepulchre of Maleck Bahamans beloued Queene … tis of foure Æquilaterall squares, eleuated eight yards high of stone.
1727. Swift, Gulliver, II. III. ii. 20. A Shoulder of Mutton, cut into an Æquilateral Triangle.
1824. Scott, St. Ronan’s, xv. A cocked hat of equilateral dimensions.
1848. Rickman, Archit., 88. The principal moulding of these doors has generally an equilateral arch.
1851. Richardson, Geol., viii. 232. The shell is consequently equilateral.
1869. Dunkin, Midn. Sky, 21. Denebola, Arcturus and Spica form very nearly an equilateral triangle.
1880. C. Taylor, Anc. & Mod. Geom. Conics, vi. 167. The Equilateral Hyperbola is … also called Rectangular.
1885. Leudesdorf, Cremona’s Proj. Geom., 269. If the hyperbola is equilateral … the asymptotes are the only pair of tangents which cut at right angles.
Hence Equilaterally adv., in an equilateral manner or form; Equilateralness.
1853. Dana, Crust., II. 704. The posterior [epimeral] equilaterally triangular.
1896. H. Holman, Educ., vi. 303. It is an idea which involves the ideas of rectilinealness, quadrilateralness, equilateralness, and equiangularity.
