The Collaborative International Dictionary of English v.0.48:

Ancient \An"cient\, a. [OE. auncien, F. ancien, LL. antianus,
   fr. L. ante before. See Ante-, pref.]
   1. Old; that happened or existed in former times, usually at
      a great distance of time; belonging to times long past;
      specifically applied to the times before the fall of the
      Roman empire; -- opposed to modern; as, ancient authors,
      literature, history; ancient days.
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            Witness those ancient empires of the earth.
                                                  --Milton.
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            Gildas Albanius . . . much ancienter than his
            namesake surnamed the Wise.           --Fuller.
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   2. Old; that has been of long duration; of long standing; of
      great age; as, an ancient forest; an ancient castle. "Our
      ancient bickerings." --Shak.
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            Remove not the ancient landmarks, which thy fathers
            have set.                             --Prov. xxii.
                                                  28.
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            An ancient man, strangely habited, asked for
            quarters.                             --Scott.
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   3. Known for a long time, or from early times; -- opposed to
      recent or new; as, the ancient continent.
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            A friend, perhaps, or an ancient acquaintance.
                                                  --Barrow.
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   4. Dignified, like an aged man; magisterial; venerable.
      [Archaic]
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            He wrought but some few hours of the day, and then
            would he seem very grave and ancient. --Holland.
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   5. Experienced; versed. [Obs.]
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            Though [he] was the youngest brother, yet he was the
            most ancient in the business of the realm.
                                                  --Berners.
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   6. Former; sometime. [Obs.]
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            They mourned their ancient leader lost. --Pope.
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   Ancient demesne (Eng. Law), a tenure by which all manors
      belonging to the crown, in the reign of William the
      Conqueror, were held. The numbers, names, etc., of these
      were all entered in a book called Domesday Book.

   Ancient lights (Law), windows and other openings which have
      been enjoined without molestation for more than twenty
      years. In England, and in some of the United States, they
      acquire a prescriptive right.
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   Syn: Old; primitive; pristine; antique; antiquated;
        old-fashioned; obsolete.

   Usage: Ancient, Antiquated, Obsolete, Antique,
          Antic, Old. -- Ancient is opposed to modern, and
          has antiquity; as, an ancient family, ancient
          landmarks, ancient institutions, systems of thought,
          etc. Antiquated describes that which has gone out of
          use or fashion; as, antiquated furniture, antiquated
          laws, rules, etc. Obsolete is commonly used, instead
          of antiquated, in reference to language, customs,
          etc.; as, an obsolete word or phrase, an obsolete
          expression. Antique is applied, in present usage,
          either to that which has come down from the ancients;
          as, an antique cameo, bust, etc.; or to that which is
          made to imitate some ancient work of art; as, an
          antique temple. In the days of Shakespeare, antique
          was often used for ancient; as, "an antique song," "an
          antique Roman;" and hence, from singularity often
          attached to what is ancient, it was used in the sense
          of grotesque; as, "an oak whose antique root peeps
          out; " and hence came our present word antic, denoting
          grotesque or ridiculous. We usually apply both ancient
          and old to things subject to gradual decay. We say, an
          old man, an ancient record; but never, the old stars,
          an old river or mountain. In general, however, ancient
          is opposed to modern, and old to new, fresh, or
          recent. When we speak of a thing that existed
          formerly, which has ceased to exist, we commonly use
          ancient; as, ancient republics, ancient heroes; and
          not old republics, old heroes. But when the thing
          which began or existed in former times is still in
          existence, we use either ancient or old; as, ancient
          statues or paintings, or old statues or paintings;
          ancient authors, or old authors, meaning books.
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The Collaborative International Dictionary of English v.0.48:

Ancient \An"cient\, n.
   1. pl. Those who lived in former ages, as opposed to the
      moderns.
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   2. An aged man; a patriarch. Hence: A governor; a ruler; a
      person of influence.
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            The Lord will enter into judgment with the ancients
            of his people, and the princes thereof. --Isa. iii.
                                                  14.
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   3. A senior; an elder; a predecessor. [Obs.]
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            Junius and Andronicus . . . in Christianity . . .
            were his ancients.                    --Hooker.
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   4. pl. (Eng. Law) One of the senior members of the Inns of
      Court or of Chancery.
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   Council of Ancients (French Hist.), one of the two
      assemblies composing the legislative bodies in 1795.
      --Brande.
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The Collaborative International Dictionary of English v.0.48:

Ancient \An"cient\, n. [Corrupted from ensign.]
   1. An ensign or flag. [Obs.]
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            More dishonorable ragged than an old-faced ancient.
                                                  --Shak.
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   2. The bearer of a flag; an ensign. [Obs.]
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            This is Othello's ancient, as I take it. --Shak.
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WordNet (r) 3.0 (2006):

ancient
    adj 1: belonging to times long past especially of the historical
           period before the fall of the Western Roman Empire;
           "ancient history"; "ancient civilizations such as those
           of the Etruscans and Sumerians"; "ancient Greece"
    2: very old; "an ancient mariner"
    n 1: a very old person [syn: ancient, antediluvian]
    2: a person who lived in ancient times

Moby Thesaurus II by Grady Ward, 1.0:

151 Moby Thesaurus words for "ancient":
   Bronze Age man, Hominidae, Iron Age man, Stone Age man, abiding,
   aboriginal, aborigine, advanced, advanced in life,
   advanced in years, age-long, age-old, aged, ageing, ageless,
   along in years, antediluvian, anthropoid, antiquated, antique,
   ape-man, archaic, auld, autochthon, better, brass hat, bushman,
   bygone, cave dweller, caveman, chronic, constant, continuing,
   dateless, diuturnal, doddering, doting, durable, earlier, early,
   elder, elderly, enduring, erstwhile, evergreen, fading, fore,
   forgotten, former, fossil, fossil man, fossilized, golden-ager,
   gray, gray with age, gray-haired, gray-headed, grey, grown old,
   hardy, higher-up, hoar, hoary, hominid, humanoid, immemorial,
   immutable, intransient, inveterate, lasting, late, long-lasting,
   long-lived, long-standing, long-term, longeval, longevous,
   macrobiotic, man of old, missing link, obsolescent, obsolete,
   of long duration, of long standing, of old, of yore, old,
   old as Methuselah, old as history, old as time, old-fashioned,
   old-time, old-timer, olden, once, onetime, past, patriarchal,
   perdurable, perduring, perennial, permanent, perpetual, persistent,
   persisting, preadamite, prehistoric, prehistoric man, prehuman,
   previous, primal, primate, primeval, primitive, primordial, prior,
   pristine, protohuman, quondam, recent, remaining, remote,
   sempervirent, senectuous, senior, senior citizen, sinking,
   sometime, stable, staying, steadfast, superannuated, then,
   timeless, timeworn, tough, traditional, troglodyte, unfading,
   venerable, vital, waning, wasting, white, white with age,
   white-bearded, white-crowned, white-haired, wrinkled, wrinkly,
   years old



Bouvier's Law Dictionary, Revised 6th Ed (1856):

ANCIENT. Something old, which by age alone has acquired some force; as
ancient lights, ancient writings.