Canalla is a fantastic, dramatic word that translates to "scoundrel" or "cad". It's a powerful, somewhat old-fashioned insult used for a dishonorable or despicable person.
In the song, Selena spits this word out right after describing how she caught her partner kissing another woman: "...eran tus labios los que la besaban, canalla" (...it was your lips that were kissing her, you scoundrel). It perfectly captures the anger and betrayal in this iconic breakup anthem, making it a truly memorable word to learn.
This song is pure drama, and it all happens over one very short phone call! It kicks off with Selena's partner calling her, trying to explain himself, but she cuts him off immediately. She has no time for his excuses because she saw him with another woman. She's incredibly direct about it, telling him, "Te vi con ella y no puedes negar / Que eran tus labios los que la besaban, canalla" (I saw you with her and you can't deny / that it was your lips kissing her, you scoundrel).
He apparently tried to pretend they were just friends, but she's not buying his claim that they were "sólo charlaban" (just talking). She is completely fed up with his "Escusas y más mentiras" (Excuses and more lies). Her message is simple and gets repeated throughout the song: "Si me vuelves a llamar / Yo te vuelvo a colgar" (If you call me again / I'll hang up on you again). This isn't a song about being sad over a breakup; it's about telling someone they messed up and aren't getting a second chance. She ends it by telling him he's not getting another opportunity because, frankly, "No vales la pena" (You're not worth it).