Descuido literally translates to an 'oversight', 'neglect', or 'moment of carelessness'. It's a word that can be used in many situations, but KAROL G gives it a very playful and strategic meaning in this song.
She sings, "Estoy esperando el primer descuido" (I'm waiting for the first slip-up), cheekily suggesting she's waiting for her crush to make a 'mistake' or have a lapse with his current girlfriend. This clever use of descuido reveals her confident personality and makes it her perfect opportunity to swoop in.
Have you ever seen someone and immediately thought, "What if?" That's exactly where Colombian superstar KAROL G is at in this song. She spots a guy who's already with someone else and spends the whole track wondering, "¿Qué hubiera sido? / Si antes te hubiera conocido" (What would it have been? / If I had met you before). She's sure that if they'd met sooner, they'd be dancing together right now, "No como amigos" (Not as friends), but as something much more.
This isn't a sad song, though. KAROL G is feeling bold and confident. She directly compares herself to his current girlfriend, saying "Ella es tímida y yo no" (She's shy and I'm not) and insists the other girl can't treat him or kiss him like she would. She's not just daydreaming; she's waiting for her chance. She even says she's just waiting for his girlfriend to slip up so she can introduce him as "mi marido" (my husband). It's a playful and direct declaration of what she wants, and she's not afraid to go after it.