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.
"Es Un Secreto" is all about mutual, unspoken attraction and total confidence. The singer claims he can read your mind without a single word: "Tengo la capacidad / Sin que me hables entenderte" ("I have the ability to understand you without you speaking"). The core of the track rests on that silent spark between two people, which he calls "un secreto de tu mirada y la mía, un presentimiento" ("a secret between your gaze and mine, a premonition"). He is not in a rush either. He repeats that it is just a matter of time ("será cuestión de tiempo"), betting that destiny and pure physical desire will pull them together eventually.
Lyrically, things get delightfully blunt once the flirting kicks into high gear. He showers her with over-the-top compliments, declaring: "Tú eres una Barbie, muñeca, princesa y no es de Mattel" ("You are a Barbie, a doll, a princess, and not from Mattel"). Calling out the toy company Mattel is a cheeky way of saying she looks flawless in real life, not made of plastic. He also throws around casual Puerto Rican reggaeton slang like "flow" to praise her natural rhythm and style, while promising that they will enjoy each other "tranquilito" (calmly and smoothly) and "lento" (slowly). It is cocky, fun, and completely sold on the idea that both of them already know how the night ends.