Fragili means "fragile" or "delicate". While it might seem like a common word, its placement in the lyrics creates a striking contrast that makes it particularly interesting.
In the song, Grignani sings, "Noi duri ma fragili / Come angeli di città" (We tough but fragile / Like city angels). This juxtaposition of "duri" (tough) and "fragili" (fragile) highlights the complex nature of the
"Angeli di città" ("Angels of the City") is about ordinary people getting through another ordinary week. Gianluca Grignani calls them "angels of the city": tough on the outside but fragile underneath, showing up for another Monday like every Monday before it.
The song moves between two images. In the verses, life is just walking the streets and greeting a new day whether you want to or not — nothing glamorous, just showing up. In the bridge, that same person imagines flying high, "where the air tastes of glory," before admitting that one day those souls in the wind come back down.
It's a song about staying grounded while still reaching for something bigger, and accepting that falling is part of the deal.