Trī-ăn'gu-lar, a.
a. [Fr. triangulaire, Pr., Sp., & Pg. triangular, It. triangolare, Lat. triangularis.] 1. Having three angles.
Sense 2. (Bot.) (a.) Flat or lamellar, and having three sides; as, a triangular leaf. (b.) Oblong, and having three lateral faces; as, a triangular stem, seed, column, and the like.
Triangular compasses, compasses with three legs for taking off the angular points of a triangle, or any three points at the same time.—Triangular numbers, the series of numbers formed by the successive sums of the terms of an arithmetical progression, of which the common difference is 1. Brande.