The Oxford Thesaurus An A-Z Dictionary of Synonyms INTRO ...

The mechanic assured me that my car would be OK.
--v. 5 approve, sanction, ratify, authorize, endorse, support,
agree to, allow, consent to, agree to, Colloq give the go-ahead
or green light to, give the thumbs up or the nod to,
rubber-stamp: A department head must OK your expense account
before you can be reimbursed.
--n. 6 approval, sanction, ratification, authorization,
endorsement, agreement, support, permission, consent: You need
an OK from the security guard to enter the restricted area.
--adv. 7 all right, satisfactorily, well (enough), adequately:
She can get along OK without me.
15.9 old...
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old adj. 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obsolete, antique, outdated, out of date, old-time, dated,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, pass‚, 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.