Acribillar literally means "to riddle with bullets" or "to pepper with bullets." It's a very strong and somewhat violent verb that isn't commonly found in everyday song lyrics, making it quite unique and memorable.
In "Fue Solo Sexo," the word is used metaphorically: "Acribillar nuestro mundo perfecto" (to riddle our perfect world). Here, it conveys the idea of completely destroying or tearing apart their seemingly perfect relationship with harsh truths and deceit, much like bullets would tear through something. This intense imagery makes the word particularly impactful in the context of a song about betrayal and the painful aftermath of a casual encounter.
Paty Cantú spends most of "Fue Sólo Sexo" rehearsing a lie before she has to say it out loud. It opens with the terms of the deal: "Decir que fue solo sexo" ("To say it was just sex") and "Y que lo nuestro eso es amor" ("And that what's ours is love"), two lines that only work together if you never stop to "pensar con el corazón" ("think with the heart"). The line "No luego decir fue solo sexo" ("No, then say it was just sex") comes back three times across the song, less like a fact than something she has to keep repeating to believe it.
The last verse is where the script breaks. She admits "Sé que fallé" ("I know I failed"), then reverses the whole premise: "No nunca fue amor fue solo sexo" ("No, it was never love, it was just sex"), followed immediately by "No el fue un error y a ti te quiero" ("No, he was a mistake and I love you"). The affair gets demoted to a mistake, and the thing she spent the whole song calling "just sex" turns out to be the real love after all.