Definition of "chu"

chu

interjection
1. (anime and manga fandom slang) The sound of a kiss.
  Quotations
  By the way, isn't it interesting that the Japanese hear the sound "chu" when someone kisses? In the US, we usually say, "smooch," "smack," "smerp," or even "swock." Now, everytime[sic] I kiss my husband, I'm listening to hear if it sounds like "chu."
  1996 August 12, Kathleen Webb, “Re: Zoicite a guy!!!”, in alt.fan.sailor-moon‎ (Usenet)
  >Eldrick Tobin - Kiss worthiness of sig pending.<chu!>Seems fine to me. ^_^
  2000 August 4, Fish Eye no Miko [username], “Re: [POLL] Which anime characters could be Ohtori students?”, in alt.fan.utena‎ (Usenet)
  movie Akio: [shoots a kiss to himself] Chu! ^.~
  2000 August 19, Verthandi, “Re: [META] Ohha! Gally desu!”, in alt.fan.utena‎ (Usenet)