嘻嘻哈哈

xīxīhāhā
  1. (ideophonic, of people) laughing and joking; laughing and talking happily; cheerful
  2. (ideophonic, of people) not having a serious attitude; facetious; frivolous
  3. laughing and joking; laughing and talking happily; cheerful
  4. not having a serious attitude; facetious; frivolous

Wiktionary

Entry Composition

=1 嘻嘻 xīxī
  1. hee hee
  2. happy
=1 嘻嘻 xīxī
  1. (onomatopoeia) laughing sound
  2. laughing sound
2 哈哈 hāhā (onom.) laughing out loud