The Collaborative International Dictionary of English v.0.48:

Alone \A*lone"\, a. [All + one. OE. al one all allone, AS. [=a]n
   one, alone. See All, One, Lone.]
   1. Quite by one's self; apart from, or exclusive of, others;
      single; solitary; -- applied to a person or thing.
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            Alone on a wide, wide sea.            --Coleridge.
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            It is not good that the man should be alone. --Gen.
                                                  ii. 18.
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   2. Of or by itself; by themselves; without any thing more or
      any one else; without a sharer; only.
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            Man shall not live by bread alone.    --Luke iv. 4.
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            The citizens alone should be at the expense.
                                                  --Franklin.
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   3. Sole; only; exclusive. [R.]
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            God, by whose alone power and conversation we all
            live, and move, and have our being.   --Bentley.
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   4. Hence; Unique; rare; matchless. --Shak.
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   Note: The adjective alone commonly follows its noun.
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   To let alone or To leave alone, to abstain from
      interfering with or molesting; to suffer to remain in its
      present state.
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The Collaborative International Dictionary of English v.0.48:

Alone \A*lone"\, adv.
   Solely; simply; exclusively.
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WordNet (r) 3.0 (2006):

alone
    adv 1: 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]
    2: without anybody else or anything else; "the child stayed home
       alone"; "the pillar stood alone, supporting nothing"; "he
       flew solo" [syn: alone, solo, unaccompanied]
    adj 1: isolated from others; "could be alone in a crowded room";
           "was alone with her thoughts"; "I want to be alone"
    2: lacking companions or companionship; "he was alone when we
       met him"; "she is alone much of the time"; "the lone skier on
       the mountain"; "a lonely fisherman stood on a tuft of
       gravel"; "a lonely soul"; "a solitary traveler" [syn:
       alone(p), lone(a), lonely(a), solitary]
    3: 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]
    4: radically distinctive and without equal; "he is alone in the
       field of microbiology"; "this theory is altogether alone in
       its penetration of the problem"; "Bach was unique in his
       handling of counterpoint"; "craftsmen whose skill is
       unequaled"; "unparalleled athletic ability"; "a breakdown of
       law unparalleled in our history" [syn: alone(p), unique,
       unequaled, unequalled, unparalleled]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "alone":
   abandoned, absolute, alienated, all alone, aloof, apart, azygous,
   barely, but, by itself, celibate, companionless, deserted,
   desolate, detached, entirely, excellent, exclusively,
   first and last, friendless, good, homeless, impair, in solitude,
   in the singular, incomparable, independently, individually,
   inimitable, insular, isolate, isolated, just, kithless, lone,
   lonely, lonesome, matchless, merely, odd, once, one and only,
   one by one, only, only-begotten, out-of-the-way, particularly,
   peerless, per se, plainly, private, purely, remote, removed,
   retired, rootless, secluded, second to none, separate, separated,
   separately, severally, simply, simply and solely, single-handed,
   single-handedly, singly, singular, singularly, sole, solely,
   solitary, solo, superior, unabetted, unaccompanied, unaided,
   unassisted, unattended, unequaled, unescorted, unexampled,
   unexcelled, unique, unmatched, unpaired, unparalleled,
   unrepeatable, unrepeated, unrivaled, unseconded, unsupported,
   unsurpassed, withdrawn, without equal



The Devil's Dictionary (1881-1906):

ALONE, adj.  In bad company.

    In contact, lo! the flint and steel,
    By spark and flame, the thought reveal
    That he the metal, she the stone,
    Had cherished secretly alone.
                                                           Booley Fito