Deleito comes from the verb deleitar, which means "to delight" or "to take great pleasure in." It's a more intense and poetic word than the more common disfrutar (to enjoy).
In the song, the singer says, "Mientras me deleito, aprovecho el momento" (While I delight myself, I take advantage of the moment). He's savoring the anticipation and the slow burn of attraction, making deleito a perfect word to describe this sensual, unhurried enjoyment.
This song is all about that electric feeling when you and someone else have a crush on each other, but nobody has said it out loud yet. It's a game of patience and confidence. The singer is absolutely sure something is going to happen, telling the girl, "Si no es hoy, mañana tal vez / Pero algún día voy a tenerte" [If not today, maybe tomorrow / But one day I'm going to have you]. He feels like he can read her mind and knows the attraction is mutual, calling it "un secreto / De tu mirada y la mía" [a secret / between your gaze and mine].
He's not just waiting around, though; he's building up the fantasy and the tension. The lyrics get pretty direct about how perfect he thinks she is, comparing her to a doll: "Tú eres una Barbie, muñeca, princesa y no es de Mattel" [You are a Barbie, a doll, a princess and not from Mattel]. It's a classic reggaeton mix of sweet talk and pure confidence, all leading up to the moment they can finally be alone together.