The word sprouter is a term used very loosely , towards a good looking girl. Often yelled out of cars windows or just to passers by . It is a term derived from the "skaters"
But used properly it is defined as a young girl blossoming into a good looking women.

A portmanteau of carpe diem, a Latin phrase that means “Seize the Day!” and DM, which stands for Direct Messages. This word means seizing the day via DMs.

A hot, young or 'fresh' girl 16-20 years old. "Sprouting" meaning that they are young and blossoming. Can also have connotations of being naive or easily preyed upon (by 18-25 year old skateboarders, who are the primary users of this term).

Someone who one thinks will be hot when they are older.

Hot girl.
In Barcelona also known as Meritxell, or MeryJane for aussies.

girls younger than you are (generally 2 years younger) who are less experienced in the art of sexuality. But are whiling to put out alot

A group of girls who "sprout" other girls into what they call "popularity". The activities they participate in include: Ruining songs for everyone by making slutty videos, Uniting for closet parties, passing out every weekend, and calling themselves the "Line Bitches". WARNING: Sprouters have been known to get caught by parents.