It's a reference to a song "Fastlane Youngstas" by Los Angeles rapper, Nipsey Hussle. It's on the album Bullets Ain't Got No Names Vol. III. The term describes a person who's been through the struggle and whose primary concern is living a gangsta life and making it on top.
Fastlane Youngstas, We Fly or We Die.
Larry: Tron's a fastlane youngsta. I love that man.
Peter: Nigga, you gay