Trasluz literally translates to "backlight" or "translucent light." It's a poetic and less common word that evokes a specific visual.
In the song, it's used in the phrase "fantasmas en la noche de trasluz" (ghosts in the translucent night). This creates a mysterious and ethereal image, suggesting a night where light filters through, making things appear hazy or indistinct, much like how one might perceive ghosts. It's a beautiful and evocative word that adds depth to the lyrics.
This song, "Vete de Mí" (Get Away From Me), is a really moving and a little heartbreaking conversation between two people at very different stages of life. The singer is talking to someone young and full of joy, someone who "llenas todo de alegría y juventud" (fills everything with joy and youth) and sees "fantasmas en la noche de trasluz" (ghosts in the dim light of night). He's telling this person to leave him, to not look at his "ramas muertas del rosal" (dead branches of the rosebush) that are withering without blooming.
It feels like he's been through a lot, saying he's "luchado contra toda la maldad" (fought against all evil) and his hands are so worn out from holding on tight that he can't even hold the other person anymore. He believes he'll be a better memory, like "la neblina del ayer" (the mist of yesterday) once he's forgotten, or like a beautiful verse "que no podemos recordar" (that we can't remember). It's a sad but beautiful way of saying goodbye, wanting the other person to experience love and dreams without being weighed down by his past.