Desgreñado translates to "disheveled" or "tousled." It's a vivid and somewhat playful word that isn't commonly found in everyday song lyrics, making it stand out.
In the song, Juan Luis Guerra uses it to describe a "sol desgreñado" (a disheveled sun) dancing with a cloud. This personification creates a charming and whimsical image, giving a human-like quality to the sun and adding a unique poetic touch to the lyrics.
Juan Luis Guerra spends the whole song pairing things off. The moon gets rosemary, dawn gets the pine forest, the wind gets the tide, even the wheat gets its trellis: "La luna con el romero" [The moon with the rosemary], "La aurora con el pinar" [The dawn with the pine forest]. Every corner of nature already has a partner, and that list is the setup for the ultimatum that follows it: "Si tú no bailas conmigo" [If you don't dance with me], "Prefiero no bailar" [I prefer not to dance]. It's merengue, so the conceit isn't subtle. It's the whole song, stacked verse after verse until it lands on the dance floor as a dare.
The pairings keep coming: basil waiting on thyme in the rosebush, a starry sky dancing over the sea, a butterfly out with "Con un granito de sal" [With a grain of salt]. By the last verse even the lily has found somebody: "Ya tiene con quien bailar" [Already has someone to dance with]. The singer is the one thing left standing still, and that's why the hook keeps coming back louder, "La noche se queda en vilo" [The night stays in suspense], waiting on the one dancer who hasn't moved yet.