Un no sé qué literally means 'an I don't know what', and it's the Spanish equivalent of the French phrase 'je ne sais quoi'. It's used to describe an appealing quality that is hard to define or put into words.
In the song, Greeicy sings that the person she's met has 'una cosita por ahí, un no sé qué' (a little something there, a certain something). She uses this charming phrase to capture the mysterious and irresistible attraction she feels.
Colombian pop singer Greeicy brings pure, instant infatuation in "Quiero +". Right from the start, she jokes that she must have done something incredible in a past life ("Algo muy bueno yo hice en la vida pasada" [Something very good I did in a past life]) just to run into this person now. The crush is so intense that she instantly scrapped all her existing plans. She playfully begs to make things permanent, asking, "¿Dónde voto, dónde firmo / Pa' quedarme toda la vida con usted?" ("Where do I vote, where do I sign to stay my whole life with you?"). Notice how she mixes the polite pronoun "usted" with romantic, flirty lines; in Colombian Spanish, using usted can feel intimate, sweet, and charming rather than strictly formal.
The chorus hits with the catchy thrill of an accidental spark: "Sin querer, te encontré / Contigo conecté / Yo no sé, pero quiero más, bebé" ("Without meaning to, I found you / With you I connected / I don't know, but I want more, baby"). Greeicy describes a chemistry so thick that time moves strangely, insisting "No es pa' tanto, es pa' siempre" ("It's not a temporary thing, it's forever"). Between daydreaming of jetting off to Paris and dancing dancehall on a street corner with salt-rimmed beer ("cerveza con sal"), the track is all about loving someone's sweet kisses ("esa boquita, preciosa, bonita y jugosa" [that mouth, precious, pretty and juicy]) and wanting to lock down that connection for good.