Synonyms for Triangular:

adj.

having three angles (adjective)
deltoid.
three (adjective)
ternary, Triadic, triple, deltoid, tripartite, trilateral, clover-like.
three-cornered (adjective)
three-sided, trilateral, triagonal.

n.

complicated, double, composite, cellular, two-ply, quadripartite, dual. circular, crosswise, arched, cruciform, domed, elliptical, corkscrew, hooked, cylindrical, conical. three-cornered (noun)
triagonal, delta-shaped.
triangular (noun)
angulate, tripartite, three-party, three-way, trilateral, three-sided, angular, many-sided, multilateral.

Other synonyms:

Other relevant words:
angulate, three-party, angular, three-sided, trilateral, tripartite, multilateral, triagonal, three-way, many-sided.

Usage examples for triangular

  1. They are rigged with one mast, which steps upon the platform, and can easily be raised or taken down; and are sailed with a latteen- sail, or triangular one, extended by a long yard, which is a little bent or crooked. – A Voyage Towards the South Pole and Round the World, Volume 1 by James Cook
  2. Beppo was assisted by the triangular recurrence of the words and their partial relationship to Italian to interpret them: 'This night. – The Complete Project Gutenberg Works of George Meredith by George Meredith
  3. All that I saw was that the thing was white and had a triangular shaped head. – The Best Short Stories of 1921 and the Yearbook of the American Short Story by Various