i Register
In some senses, trigon is marked as rare, historical. Watch for register when choosing this word.
noun
A triangle.
An ancient triangular harp of Oriental origin which had four strings and was often used for banquet music. Also called sabbeka, sackbut, sambuca.
A division consisting of three star signs.
The Cancer trigon is composed of Cancer, Scorpio and Pisces
A trine; an aspect of two planets distant 120 degrees from each other.
In the horoscope of Christ's nativity.[…]Whether a trigon or no, this tetragon I am sure there was.
An old ball game played by three people standing in a triangular formation. (See Wikipedia's entry for the game)