Triangular crab

Triangular Tri*an"gu*lar, a. [L. triangularis: cf. F. triangulaire.] 1. Having three angles; having the form of a triangle. [1913 Webster]

2. (Bot.) Oblong or elongated, and having three lateral angles; as, a triangular seed, leaf, or stem. [1913 Webster]

{Triangular compasses}, compasses with three legs for taking off the angular points of a triangle, or any three points at the same time.

{Triangular crab} (Zo["o]l.), any maioid crab; -- so called because the carapace is usually triangular.

{Triangular numbers} (Math.), the series of numbers formed by the successive sums of the terms of an arithmetical progression, of which the first term and the common difference are 1. See {Figurate numbers}, under {Figurate}. [1913 Webster]