the horrible japanese pronounciation of "love" except with super heavy accents on "la" and "vu", thus making it RA-BU. It is a horribly ridiculous and embarrassing term couples use when they're mushy and uberly happy. The word is often used twice consecutively for an extra emphasis.
"God, they're so frickin rabu rabu."
"How are you guys doing lately?" "Us, oh we're super rabu rabu!"