The sound one makes when a subject of a romantic nature arises in conversation.
It can be accompanied by a light flutter in the heart.
Extended periods of joy suppression can climax with an explosive rush of conjoined 2uhu2s, literally expressed as 2uhu2uhu2uhu2uhu2uhu2uhu2...
The '2' is an Arabish letter. In 2uhu2, it is pronounced as the double 'o' at the start of "oops". The '2' at the end can be treated as a silent '2'.
Ron Weasley: I am flying out of town to visit my fiance next week. I am so excited!
Ron Weasley's brother with big smile on face: 2uhu2!
Ron Weasley: We (man, fiance, and brother) are all travelling to Vegas to meet next month!
Ron Weasley's fiance: Who is going to Vegas?
Ron Weasley: Whoooo??
Ron Weasley's brother: Whoooooooo??
Ron Weasley's fiance: Whoooooooooooooooooooo???
Ron Weasley's brother: 2uhu2uhu2uhu2uhu2uhu2uhu2...