Scontrosa translates to "sullen," "cranky," or "grumpy" in English. It's an interesting word choice because it describes a prickly, difficult personality rather than the usual sweet or seductive traits celebrated in pop songs.
In the song, ANNA repeats this word to describe a woman who, despite her beauty, has a difficult attitude, singing "Mhm, scontrosa, baby è scontrosa" ("Mhm, prickly, baby she's prickly"). The repetition turns the word almost into a badge of pride rather than an insult.
The first half of this song is a straight beauty catalogue. "Quelle gambe lunghe ad ogni passo fanno un metro" (those long legs cover a meter with every step), lips so glossy they look like glass, the whole subway car turning around when she walks through. Then ANNA drops two lines that reframe all of it. The girl does her lipstick "specchiandosi nella lama" (using a blade as a mirror), and "a casa ha un padre con problemi di droga" (at home she has a father with a drug problem). That is the whole explanation for the title, and it lands before the first chorus, with no build-up.
Scontrosa means prickly, the sort of person who answers everything short. The hook keeps needling her about it: "Con 'sto atteggiamento, baby, chi ti sposa?" (with that attitude, baby, who's going to marry you?), a question ANNA never bothers to answer, because the verse already did. Half the hook slides into Spanish so that "hermosa" and "calle" can rhyme with "scontrosa" and "nervosa", and that chain of -osa endings is most of what holds the chorus together. The track is under two minutes and the hook takes up close to half of it.