grown man; full-grown man; adult male
Emphasizes physical maturity and strength; often used in contexts where a man is expected to be capable or brave, or when contrasting with a child or woman.
It's pathetic for a grown man to cry.
It's so heavy that it takes three full-grown men to carry it.
Compound of 大 (だい, 'big') + の (possessive particle) + 男 (おとこ, 'man'). The 大の pattern is used in a few set phrases to mean 'full-fledged' or 'great'.