E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The junction of three signs. The zodiac is partitioned into four trigons, named respectively after the four elements; the watery trigon includes Cancer, Scorpio, and Pisces; the ficry, Aries, Leo, and Sagittarius; the earthy, Taurus, Virgo, and Capricornus; and the airy, Gemini, Libra, and Aquarius.