Desenfoque means 'to lose focus' or 'to blur'. It's a less common verb in everyday conversation, making it stand out in the lyrics.
In the song, Nyno Vargas sings, "Yo pierdo la cabeza yo me desenfoco" (I lose my head, I lose focus). He uses this word to express how overwhelmed he is by the woman's presence, to the point where he can't concentrate on anything else. It vividly portrays the intensity of his feelings.
Nyno Vargas is totally smitten in "Loco"! This song is all about that intense, head-over-heels feeling when someone just completely captivates you. He sings about seeing her dancing and getting that familiar feeling of wanting her in his arms, saying, "No he perdido esa ilusiĂłn" [I haven't lost that hope].
He's so open about his feelings, giving her a piece of his heart and admitting, "Y es que tĂș me tienes loco, loquito loco de amor" [And it's that you drive me crazy, crazy in love]. He's obsessed with everything about her: "Tu pelo, tu sonrisa, tu mirada tierna" [Your hair, your smile, your tender gaze]. Every time she dances, he feels like she lifts him up. He even recalls the night they met, and how her voice made him feel that desire to be with her. He's not going to waste this chance, and he's definitely not letting go, even asking, "Dime tĂș quĂ© puedo hacer, si por ti estoy loco mujer" [Tell me what I can do, if I'm crazy for you, woman].