n. A male who is on their way to becoming a man, but still too young to be considered one. Usually at or between the ages of 10 to 15, give or take a couple years depending on maturity.
My little brother is growing up, but he's still just a man-cub.
A male child that does something or resembles a grown man in either action or appearance.
"Look at him in those skinny jeans, he's such a man-cub!"