Disparatado translates to "absurd" or "nonsensical." It's a less common, more evocative word than simply saying something is "crazy" or "ridiculous."
In the song, Bunbury uses it to describe the current state of the world, contrasting it with a "century before." He sings, "Hoy todo es tan disparatado" (Today everything is so absurd), highlighting a feeling of disillusionment and a sense that things have gone awry in modern times. This word perfectly captures the song's critical and reflective tone.
Bunbury's "De Un Siglo Anterior" [From a Previous Century] is a fascinating look at how someone from a different era might feel in our modern world. He starts by saying, "Yo Vengo de un siglo anterior / De contradicción / Y revolución" [I come from a previous century / Of contradiction / And revolution], immediately setting up this idea of being out of sync. He remembers a time when being "raro es normal" [weird is normal] in youth, and even being "El loser con más dignidad / De la ciudad" [The loser with the most dignity / In the city] was a kind of identity.
Fast forward to today, and he sees a world of "Vulgaridad / Y economía de la atención" [Vulgarity / And economy of attention]. It's a place where "Todo es tabú" [Everything is taboo] and there's a "bancarrota espiritual / Y la esclavitud / Del que adora al capataz / A voluntad" [spiritual bankruptcy / And the slavery / Of one who adores the foreman / Willingly]. He feels like an "Animal en vías de extinción" [Animal on the verge of extinction], clinging to the same convictions about summer desires and winter dreams that guided him before. It's a really sharp contrast between his past and the present, and you can feel his sense of being a relic in a world that's moved on.