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.
If you have ever caught someone red-handed and listened to them scramble for a terrible excuse, this track is your ultimate anthem. Selena opens the song right in the middle of a phone argument where her cheating ex begs, "Antes de que me cuelgues nomás déjame explicar que..." [Before you hang up on me, just let me explain that...]. She shuts that down immediately. There is zero room for debate because she literally watched him kissing another woman with her own eyes ("eran tus labios los que la besaban" [it was your lips kissing her]). She even hits him with the insult "canalla" [scoundrel/jerk], calling out his ridiculous attempt to pretend they were "sólo charlaban" [just chatting].
What makes this track so satisfying is her total lack of hesitation. She is completely done with the drama, telling him straight up: "Si me vuelves a llamar, yo te vuelvo a colgar" [If you call me again, I'll hang up on you again]. There are no second chances ("Otra oportunidad no te la doy" [Another chance I won't give you]) because, in her words, "No vales la pena" [You're not worth it]. It is blunt, energetic, and gives you the exact words you need when you want to hang up on someone who refuses to own up to their mess.