笄

jī
  1. 15 years old
  2. hairpin for bun

CEDICT

  1. (historical) hairpin of women, perhaps made of bamboo
  2. (historical, of a woman) to become an adult at age 15 and start wearing a hairpin
  3. hairpin of women, perhaps made of bamboo
  4. to become an adult at age 15 and start wearing a hairpin

Wiktionary

古人盘髮髻所用的簪。

重編國語辭典

Containing this entry

及笄 jíjī to reach marriageable age (a girl's fifteenth birthday)
笄冠 jīguān to have just attained maturity (traditional)
笄年 jīnián beginning of maturity (of a girl)
笄蛭 jīzhì a kind of earthworm