Acorralado translates to "cornered" or "trapped." It's a vivid and somewhat dramatic word that paints a clear picture of a difficult situation.
In the song, Alfredo Olivas uses it to describe the feeling of being completely out of options in a relationship. He sings, "Es evidente que estoy más que acorralado" (It's evident that I'm more than cornered), conveying a sense of desperation and being stuck with no way out in his romantic struggles.
Alfredo Olivas's "Medalla De Plata" is a really direct and emotional song about a guy who's desperately trying to hold onto a relationship that's clearly ending. He feels like he's "Tan cerca de perderte, tan lejos de olvidarte" [So close to losing you, so far from forgetting you], and he's doing everything he can to keep her, even though she's already made up her mind. He describes himself as "más que acorralado" [more than cornered] and says this "jueguito ya me tiene sin salida" [little game has left me with no way out].
He's not interested in being friends or getting a consolation prize. He bluntly tells her, "No me beses la mejilla como premio de consolación" [Don't kiss my cheek as a consolation prize] and "No me cuelgues la medalla y menos si es de plata" [Don't hang the medal on me, especially if it's silver]. He'd rather she be honest and "Pon las cartas sobre la mesa" [Put the cards on the table] to see if there's any way to negotiate a second option. He even says, "Mas ni piedad ni compasión, porque eso si que mata" [But neither pity nor compassion, because that really kills]. It's a powerful look at a man facing the end of a relationship, wanting honesty over false kindness.