私信

sīxìn
  1. private correspondence; personal letter
  2. (computing) personal message (PM); to message sb

CEDICT

computing

Entry Composition

1 私 sī
  1. personal
  2. private
  3. selfish
2 信 xìn
  1. letter
  2. mail
  3. to trust
  4. to believe
  5. to profess faith in
  6. truthful
  7. confidence
  8. trust
  9. at will
  10. at random

classifier: 封