1 elderly, ageing, aged, advanced in years or age, long-lived, past one's prime, grey, full of years, getting on (in years), hoary, superannuated, Colloq over the hill, past it:
Bill is too old to continue working in the mine.
2 ancient, antiquated, antediluvian, fossil, prehistoric, Noachian, obsolete, antique, outdated, out of date, old-time, dated, archaic, stale, out-moded, passé, Literary Ogygian:
The archaeological dig has turned up some interesting old artefacts.
3 time-worn, decayed, dilapidated, ramshackle, disintegrated, crumbling, shabby, worn out, dusty, broken-down, tumbledown, disused, unused, cast off, cast aside:
They have torn down the old mill near the river.
4 long-standing, well-established, enduring, lasting, age-old, time-honoured:
It is hard to see an old friendship die.
5 former, olden, bygone, early, primordial, primitive:
In the old days, it took a week to travel from London to Edinburgh.
6 previous, preceding, prior, former, quondam, erstwhile, one-time, ex-:
The West End was my old stamping-ground when I lived in London.
7 experienced, veteran, practised, (well-)versed, knowledgeable, proficient, accomplished, adept, skilled, expert, old-time:
Charles is an old hand at steam engines.
8 dear, beloved, loved, esteemed, valued, precious, well-known, intimate, close, familiar:
Penelope is an old friend of the family's.