Inimaginable translates to "unimaginable" or "unthinkable." It's a strong adjective that conveys a sense of boundless possibility and extreme effort.
In the song, the singer declares, "Yo haría lo inimaginable" (I would do the unimaginable) to express the depth of his love and devotion. He's willing to go to extraordinary lengths, beyond what one could even conceive, just to be with the person he loves. This word beautifully captures the passionate and all-encompassing nature of his feelings.
Joss Favela's "La Magia De Tus Ojos" is a passionate declaration of love and devotion. He's completely captivated by someone's eyes and lips, so much so that he'd become anything for them: "Yo me volvería tu esclavo, Tu mendigo, tu payaso" [I would become your slave, your beggar, your clown]. He'd do the unimaginable, even "Cruzaría todos los mares" [I would cross all the seas], just to have their love.
He explains this intense feeling by saying he'd never seen such beauty before, claiming "antes de ti, no conocía las princesas" [before you, I didn't know princesses]. For him, this person is the reason he believes in destiny, and he wants every tomorrow to be with them. It's a sweet, over-the-top expression of being utterly smitten!