Veliero translates to "sailboat" or "sailing ship". It's a beautiful and somewhat evocative word that isn't as common as more basic terms for boats.
In the song, it appears in the line "Una rondine si posa su un veliero" (A swallow lands on a sailboat). This imagery adds a touch of poetic whimsy and a sense of journey or freedom, fitting the theme of the "girl of the future" who is exploring the world.
"La Ragazza Del Futuro" imagines a woman who feels almost like a symbol of hope, a "girl of the future" who has seen extraordinary things and carries the wonder and exhaustion of a changing world in her eyes.
The singer finds her adrift: leaning over a wall, lost on a street, scared on an airport escalator, unsure of the ground under her feet. He doesn't try to fix her. He just asks her to stay, to dance, to sing, and to keep loving even when it hurts.
By the end the song becomes an anthem for anyone who feels unsteady in an uncertain world. Its refrain, dance, sing, don't stop, love and feel the pain, is less a description of one woman than encouragement to face the future without giving up.