1. a. Having four angles, and consequently four sides; tetragonal.

¹ Source: wiktionary.com

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Below you will find example usage of this term as found in modern and/or classical literature:

1. Projective Geometry by Oswald Veblen, John Wesley Young (1910)
"CHAPTER IV HARMONIC CONSTRUCTIONS AND THE FUNDAMENTAL THEOREM OF PROJECTIVE GEOMETRY 30. The projectivity of quadrangular sets. ..."

2. Projective Geometry by Oswald Veblen, John Wesley Young (1910)
"The projectivity of quadrangular sets. We return now to a more detailed discussion of the notion of quadrangular sets introduced at the end of Chap. II. ..."

3. A Descriptive Catalogue of the Antiquities in the Museum of the Royal Irish by Royal Irish Academy Museum, William Robert Wilde (1863)
"539, quadrangular, semilunar edge, large broad loop, everted edge to socket; ... 547, defective for about 1f inch at cutting edge, quadrangular, ..."

4. The Strains in Framed Structures, with Numerous Practical Applications to by Augustus Jay Du Bois (1883)
"46 become very long, we may divide them up, and thus obtain the double quadrangular system of Fig. 47(0), or, as it is called sometimes, ..."

5. Graphics for Engineers, Architects, and Builders: A Manual for Designers by Charles Ezra Greene (1879)
"Double quadrangular Truss. — When, from length of span and corresponding economical ... The name of double quadrangular truss may be used to designate it, ..."

6. The Theory and Practice of Modern Framed Structures, Designed for the Use of by John Butler Johnson, Charles Walter Bryan, Frederick Eugene Turneaure, William Spaulding Kinne (1910)
"ANALYSIS OF A quadrangular TRUSS 59. Analysis of a quadrangular Truss.—Truss shown in Fig. 6 (a). Span of 72 feet; pitch of roof, %. Trusses 16 feet apart. ..."

7. The Antiquary (1873)
"The fortress as it now stands is nearly quadrangular in form, ... The castle thus built is stated to have been in " the usual quadrangular form," and to ..."

8. Trusses and Arches Analyzed and Discussed by Graphical Methods by Charles Ezra Greene (1879)
"Double quadrangular Truss. — When, from length of span and corresponding economical ... The name of double quadrangular truss may be used to designate it, ..."