Astrological boundary dividing signs of the zodiac (4)

I believe the answer is:

cusp

(Other definitions for cusp that I've seen before include "Pointed end where two curves meet" , "Horn of moon" , "Point (e.g. of tooth)" , "One point of a crescent moon" , "Point of transition, brink" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.