Cusp, Cusp Line, House Cusp

The line that separates the houses and indicates the beginning of a house. Alternate: The line of division between two Houses on the horoscope (House cusp). A birth planet is stronger when it is on the cusp than when it is in the last degrees of a House. The angular cusps are doubtless the sharpest.

Definition of House Cusp:

The zodiacal degree at which a house begins.

Are Zodiac Sign Cusps a Real Thing?

The idea of “born on the cusp of two signs” is a modern invention of popular astrology and has no precedent in ancient or medieval astrology literature. Every surviving ancient or medieval astrological source uses “cusp” strictly for the starting point of a house, never for the edge between two signs.

When early astrologers meant 0° of a sign, they simply wrote “first degree of Aries,” or “0° Taurus.” There was no hint of overlap or blending.

Classical era astrologers spoke of each 30-degree sign as an independent “temple,” ruled by a planet. There was no doctrine that the influence softens or overlaps at the edges; on the contrary, the exact borders between signs were needed for determining dignities and terms.

The idea of sign cusps (like “Aries/Taurus cusp”) showed up only in late 19th-century and 20th-century popular astrology magazines and newspapers.

The sun is never recognized as being in two signs simultaneously, so you cannot have two sun signs.