Indecorosa translates to "indecorous" or "improper." It's a more formal and less common word than its synonyms, making it stand out in the lyrics.
In the song, the singer reflects on a past encounter, wondering, "Si es una cita indecorosa o como aquella vez" (If it's an improper date or like that time). This word adds a layer of intrigue, hinting at a rendezvous that might have been scandalous or unconventional, making the listener curious about the nature of their relationship.
The whole song is one man at a table trying to get a bottle taken away from him. "Ya no me pasen la botella, por favor" (Please don't pass me the bottle anymore) is the first line, and the reason arrives in the second: "Con el Don Julio se me activa el desamor" (With the Don Julio, the heartbreak switches on). Tequila is supposed to be the cure here. Instead it is the trigger, and he says so flatly: "Con cada trago me da más dolor" (With every sip it hurts me more). By "Media botella y ya pienso y tras ella" (Half a bottle in and I'm already thinking, and going after her), the drinking has turned into a countdown.
What he remembers is oddly specific, which is the best thing about the lyrics: roses that "Combinaban con tu hermosa piel" (matched your beautiful skin), a reflection in a window he still watches for every day, "Besarte el cuello y como siempre ver la lluvia caer" (kissing your neck and, like always, watching the rain fall). He has given up on the polite version too, because "A mí no me funciona" (It doesn't work for me) to say everything is fine. So the closing verse takes the opening request and turns it into a plan: "Así que por favor ya no me pasen la botella" (So please, don't pass me the bottle anymore), "Porque quiero ir tras de ella" (Because I want to go after her). He is not putting the glass down to sober up. He is putting it down because he has somewhere to be.