immature Antonyms

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