From Wiktionary, the free dictionary
Circled digit 9.
⑨
- (astronomy, no fill) The asteroid 9 Metis.
- (go) The ninth (white or black) stone played in a position.
- See ①
- (astronomy, dated):
⑨ • (maru-kyū)
- The number 9 enclosed in a circle, used in enumerating lists.
A diagram of gameplay in the manual of Phantasmagoria of Flower View labelled Cirno with the legend "⑨ (⑨)" and the key "9. Idiot".
⑨ or ⑨ or ⑨ • (maru-kyū or baka or kyū)
- (Can we verify(+) this sense?) (fandom slang, endearing) The Touhou character Cirno, known affectionately as an idiot.
2008, “⑨destiny ~ ずっとチルノのターン”, in bit (lyrics), Rebirth, performed by Silver Forest:
- ⑨って言うな~
- Marukyū tte iu na~
- Don't call me nineball~