Traicionera means 'treacherous' or 'traitorous'. It's a strong word that describes someone who betrays trust or is disloyal.
In the song, the singer reflects on a past situation where the person he desires was with someone else. He sings, "Y no se te dio lo de ser traicionera" (And you didn't get to be treacherous), implying that she chose not to betray her previous partner, even though he might have wished she had. This word adds a layer of dramatic tension and unfulfilled desire to the narrative.
Have you ever had a crush on someone and imagined exactly how you'd win them over? That's what Sebastián Yatra sings about in "Los Domingos"! He's had a detailed plan in his mind since November 16th, just waiting for the right moment. He's been patient, but now that fate has brought them face to face, all he needs is a "Sí" [Yes]!
His plan is adorable and super romantic. It starts with a love song and ends with a casual "¿Hoy qué vas a hacer?" [What are you doing today?]. He dreams of taking her to places no one else has, just to see her again. He'd even invent that she left a kiss behind, asking "Dime qué día te lo puedo devolver" [Tell me what day I can give it back to you]. He hopes she'd reply, "Ahora mismo, corazón" [Right now, my love], leading to a relationship "De esas que no acaban los domingos" [Of those that don't end on Sundays]. He's been waiting for her to be single, and now that she is, he's ready to put his plan into action. It's all about that hopeful, exciting feeling of a new romance!