The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, a. [OE. only, anly, onlich, AS. [=a]nlic, i.e.,
   onelike. See One, and Like, a.]
   1. One alone; single; as, the only man present; his only
      occupation.
      [1913 Webster]

   2. Alone in its class; by itself; not associated with others
      of the same class or kind; as, an only child.
      [1913 Webster]

   3. Hence, (figuratively): Alone, by reason of superiority;
      preeminent; chief. "Motley's the only wear." --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, adv. [See Only, a.]
   1. In one manner or degree; for one purpose alone; simply;
      merely; barely.
      [1913 Webster]

            And to be loved himself, needs only to be known.
      --Dryden.
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   2. So and no otherwise; no other than; exclusively; solely;
      wholly. "She being only wicked." --Beau. & Fl.
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            Every imagination . . . of his heart was only evil.
                                                  --Gen. vi. 5.
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   3. Singly; without more; as, only-begotten.
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   4. Above all others; particularly. [Obs.]
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            His most only elected mistress.       --Marston.
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The Collaborative International Dictionary of English v.0.48:

Only \On"ly\, conj.
   Save or except (that); -- an adversative used elliptically
   with or without that, and properly introducing a single fact
   or consideration.
   [1913 Webster]

         He might have seemed some secretary or clerk . . . only
         that his low, flat, unadorned cap . . . indicated that
         he belonged to the city.                 --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

only
    adv 1: and nothing more; "I was merely asking"; "it is simply a
           matter of time"; "just a scratch"; "he was only a child";
           "hopes that last but a moment" [syn: merely, simply,
           just, only, but]
    2: without any others being included or involved; "was entirely
       to blame"; "a school devoted entirely to the needs of problem
       children"; "he works for Mr. Smith exclusively"; "did it
       solely for money"; "the burden of proof rests on the
       prosecution alone"; "a privilege granted only to him" [syn:
       entirely, exclusively, solely, alone, only]
    3: with nevertheless the final result; "He arrived only to find
       his wife dead"; "We won only to lose again in the next round"
    4: in the final outcome; "These news will only make you more
       upset"
    5: except that; "It was the same story; only this time she came
       out better"
    6: never except when; "call me only if your cold gets worse"
       [syn: only, only if, only when]
    7: as recently as; "I spoke to him only an hour ago"
    adj 1: being the only one; single and isolated from others; "the
           lone doctor in the entire county"; "a lonesome pine"; "an
           only child"; "the sole heir"; "the sole example"; "a
           solitary instance of cowardice"; "a solitary speck in the
           sky" [syn: lone(a), lonesome(a), only(a),
           sole(a), solitary(a)]
    2: exclusive of anyone or anything else; "she alone believed
       him"; "cannot live by bread alone"; "I'll have this car and
       this car only" [syn: alone(p), only]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "only":
   absolute, after a fashion, alone, appreciably, at any rate,
   at best, at least, at most, at the least, at the most,
   at the outside, at worst, azygous, barely, but, celibate,
   companionless, comparatively, contrariwise, detectably, entirely,
   exclusive, exclusively, fairly, first and last, however, impair,
   in a manner, in a way, in part, in some measure, incomparable,
   incompletely, inimitable, integrally, irreducibly, just, leastwise,
   lone, matchless, merely, mildly, moderately, modestly,
   not comprehensively, not exhaustively, odd, on the contrary, one,
   one and only, only-begotten, part, partially, particular, partly,
   peerless, plainly, pro tanto, purely, relatively, separate, simply,
   simply and solely, single, singly, singular, so far, sole, solely,
   solitary, solo, somewhat, thus far, to a degree, to some degree,
   tolerably, totally, transcendent, unaccompanied, unanalyzably,
   unattended, undividedly, unequaled, unexampled, unique, unmatched,
   unpaired, unparagoned, unparalleled, unrepeatable, unrepeated,
   unrivaled, visibly, wholly, yet