Also, tween, tweeny. a youngster between 10 and 12 years of age, considered too old to be a child and too young to be a teenager. She is part of a new crop of tween starlets who have entered the awards season dress derby at ages younger than ever before. Fashion's 'It' Girls Get Younger Isabel Wilkinson February 3, 2011. With Hannah Montana long gone, a new legion of tween TV shows has risen.