Dura literally translates to "hard" or "tough". However, in the context of this massive reggaetón hit, Daddy Yankee uses it as slang to describe a woman who is on another level.
Calling someone dura means she's incredibly attractive, confident, strong, and essentially a "badass". It's a huge compliment that goes beyond just physical appearance, celebrating her powerful presence. This is a perfect example of how one word can have a completely different, vibrant meaning in colloquial Spanish!
Daddy Yankee's "Dura" is a pure, high-energy compliment to a woman who catches his eye. The whole song is built around the word dura, which literally means "hard," but here it's slang for looking amazing, being tough, and just being on another level. He sees her and feels he just has to say something: "Perdóname, te lo tenía que decir" (Forgive me, I had to tell you). He's not subtle about it, rating her a "veinte de diez" (twenty out of ten) and calling her "la máquina de baile" (the dancing machine).
He keeps piling on the praise with some pretty funny and bold lines. He tells her, "Si fuera un delito eso de que estás hermosa / Te arresto en mi cama y te pongo las esposas" (If being beautiful were a crime / I'd arrest you in my bed and put handcuffs on you), which is a classic, over-the-top reggaeton pickup line. He even says "Se cae el Internet cuando subes una foto" (The internet breaks when you upload a photo). It's a song that's all about celebrating a woman's confidence, beauty, and power with zero hesitation.