Impaciencia translates to "impatience." It's a strong and relatable emotion that drives much of the song's narrative.
In "Santa Lucía," the singer expresses a deep longing and frustration because he knows everything about someone but hasn't met them. He sings, "Me devora la impaciencia" (Impatience devours me), vividly conveying his overwhelming desire to finally meet this mysterious person. This word captures the core tension and yearning of the lyrics.
Aleks Syntek is singing to someone he has never actually met. He has watched her from a distance long enough to invent a whole relationship in his head: "Yo se todo de tu vida, y sin embargo, no conozco ni un detalle de ti" [I know everything about your life, and yet I don't know one detail about you]. The phone calls that never come and the fear of "Tanto loco que anda suelto" [so many crazy people running loose] out there are what's keeping her at arm's length, in his telling.
By the bridge he stops circling and starts asking directly, line by line: "Dame una cita, vamos al parque, entra en mi vida" [Give me a date, let's go to the park, enter my life]. The title comes back as a kind of chant rather than an explanation — "Santa Lucia Santa Lucia, oh Santa Lucia" — a name he repeats the way you repeat a wish, hoping saying it enough times will make it happen.