From Longman Dictionary of Contemporary Englishon the cuspon the cuspROAsomeone who was born on the cusp was born near the time when one star sign ends and another begins → cusp
Examples from the Corpus
on the cusp• They will be on the cusp of puberty.• Sing Sing seems constantly on the cusp of chaos.• With plans to add another 100 staff by April, it is on the cusp of breaking into the big league.• Claude Cheever, a young man on the cusp of 20.• Death becomes him, for ever frozen in time as a complex and charismatic 24-year-old on the cusp of greatness. 