小弟弟

xiǎodìdi
  1. little brother
  2. little boy
  3. (coll.) penis

CEDICT

colloquial

Entry Composition

1 小弟 xiǎodì
  1. little brother
  2. I, your little brother (humble)
2 弟 dì
  1. younger brother
  2. junior male
  3. I (modest word in letter)