Short for the word, Delusional, a South African phrase to indicating that you are acting like you're clueless, or "dom"
Megan: Yoh Valdo, I have a huge crush on The Weeknd and i am 100% sure that he has a crush on me and we're going to get married and have 3 kids...
Valdo: Woah, let me stop you there on your Delulu dreams, this man doesn't even know you exist, stop being Delulu!!