Wiktionary
underaged
a. underage; being or occurring below the legal age for a given activity.
Usage examples of "underaged".
They popped the Short girl in September '43 for underaged drinking, sent her home to her mother in Massachusetts.
Two are dead of syphilis, three were underaged and left the state as a probation stipulation, two I couldn't get a line on.
He had probably called Shad Harper, that underaged son of a bitch who had the office across the hallway from Eleanor's.
Again, her children brought up the subject of their tiny, underaged and helpless offspring.
She was bad with ages when it came to the underaged, but she figured maybe eight.