Vaivén is a beautiful Spanish noun that describes a rhythmic, back-and-forth movement, like swinging or swaying. It's a much more poetic and specific word than the more common 'movimiento' (movement).
In the song, Romeo Santos sings "El vaivén de tus caderas quiero sentir" (I want to feel the swaying of your hips). He uses this evocative word to capture the hypnotic and sensual rhythm of his dance partner, painting a vivid picture of the scene on the dance floor.
Romeo Santos is known as the King of Bachata, but this song is all about a different kind of dance. The title itself, "Sexo Con Ropa," tells you exactly what's on his mind: sex with clothes on. He's not singing about romance; he's describing an intense, immediate physical attraction to someone on the dance floor. The whole song is built around the idea that dancing can be so intimate and heated that it becomes its own kind of sexual experience.
He sets the scene with a simple look: "Ya con una mirada / Dices mucho" [With just a look / You say a lot]. From there, it's a direct invitation to turn up the heat. He sings about how "el baile nos excite" [the dance excites us] and wants to "turn this dance into sex." He gets incredibly blunt, asking for permission while also stating his intentions with lines like "Mami, I'll fuck you on the dancefloor if you let me." It's a song about giving in to that raw, electric feeling when two people connect through music and movement, even if it means breaking the rules.