Dictionary

big boy en · NOUN

Used other than figuratively or idiomatically: see big, boy.
(idiomatic) A large object or person.
- I've been dying to get behind the wheel of this big boy.
(idiomatic, informal) A male child who is considered mature enough for some purpose.
- You're a big boy now, and big boys go to school.
(idiomatic, informal) An adult male, considered to be sufficiently mature and independent.
- He is a big boy and can take care of himself.
- Coordinate term: big girl
(plural-normally) One who is in a dominant position, such as in business, elite sport, etc.
- He started a small manufacturing plant, but he couldn't compete with the big boys.
- The prize now for Larne is massive… something in the region of £3million. They are the envy of every other Irish League club by forcing their way in with the big boys in the UEFA Conference League. 2024 August 29, Alex Mills, “Larne headed for Conference League group stages as Andy Ryan hat-trick secures historic Play-Off joy”, in Belfast Telegraph:

Spelling	Features	Labels	Source
big boys	Number=Plur		lexicographic

pl duży chłopiec (An independent adult male) · fi iso poika (An independent adult male) · fr grand garçon (An independent adult male)