immature Antonyms

mature senior septuagenarian sophisticated suave superannuated tinned venerable grownup fully grown age-old older precocious senile senescent prime prior ready refined relic ripe ripened ritualistic salted sealed of age ageing timeworn of a certain age older than dirt old time overblown past it silver-haired streetwise agile enough well-versed as old as the sea extremely old not long for this world over the hill drop-kick white-haired long-standing rubbery one-time geriatric doddering doddery long in the tooth