I was listening to Jagjit Singh singing the famous ghazal aahista aahista, and there was this line, sawaal e wasl par unko udu ka khauf hai itna, that Jagjit ji began to explain. Here is the meaning for you.
Sawaal-e-wasl was the question of meeting. In his words, when you ask for a date, that is sawaal-e-wasl. Udu is a rival. In his words again, there is a villain in every movie, he is Udu, [or Udoo]. [I am guessing we're talking about movies which have a villain fighting for the girl.] He also tells us that even an enemy can be called Udu.