The Collaborative International Dictionary of English v.0.48:

Mean \Mean\, n.
   1. That which is mean, or intermediate, between two extremes
      of place, time, or number; the middle point or place;
      middle rate or degree; mediocrity; medium; absence of
      extremes or excess; moderation; measure.
      [1913 Webster]

            But to speak in a mean, the virtue of prosperity is
            temperance; the virtue of adversity is fortitude.
                                                  --Bacon.
      [1913 Webster]

            There is a mean in all things.        --Dryden.
      [1913 Webster]

            The extremes we have mentioned, between which the
            wellinstracted Christian holds the mean, are
            correlatives.                         --I. Taylor.
      [1913 Webster]

   2. (Math.) A quantity having an intermediate value between
      several others, from which it is derived, and of which it
      expresses the resultant value; usually, unless otherwise
      specified, it is the simple average, formed by adding the
      quantities together and dividing by their number, which is
      called an arithmetical mean. A geometrical mean is the
      nth root of the product of the n quantities being
      averaged.
      [1913 Webster]

   3. That through which, or by the help of which, an end is
      attained; something tending to an object desired;
      intermediate agency or measure; necessary condition or
      coagent; instrument.
      [1913 Webster]

            Their virtuous conversation was a mean to work the
            conversion of the heathen to Christ.  --Hooker.
      [1913 Webster]

            You may be able, by this mean, to review your own
            scientific acquirements.              --Coleridge.
      [1913 Webster]

            Philosophical doubt is not an end, but a mean. --Sir
                                                  W. Hamilton.
      [1913 Webster]

   Note: In this sense the word is usually employed in the
         plural form means, and often with a singular attribute
         or predicate, as if a singular noun.
         [1913 Webster]

               By this means he had them more at vantage.
                                                  --Bacon.
         [1913 Webster]

               What other means is left unto us.  --Shak.
         [1913 Webster]

   4. pl. Hence: Resources; property, revenue, or the like,
      considered as the condition of easy livelihood, or an
      instrumentality at command for effecting any purpose;
      disposable force or substance.
      [1913 Webster]

            Your means are very slender, and your waste is
            great.                                --Shak.
      [1913 Webster]

   5. (Mus.) A part, whether alto or tenor, intermediate between
      the soprano and base; a middle part. [Obs.]
      [1913 Webster]

            The mean is drowned with your unruly base. --Shak.
      [1913 Webster]

   6. Meantime; meanwhile. [Obs.] --Spenser.
      [1913 Webster]

   7. A mediator; a go-between. [Obs.] --Piers Plowman.
      [1913 Webster]

            He wooeth her by means and by brokage. --Chaucer.
      [1913 Webster]

   By all means, certainly; without fail; as, go, by all
      means.

   By any means, in any way; possibly; at all.
      [1913 Webster]

            If by any means I might attain to the resurrection
            of the dead.                          --Phil. iii.
                                                  ll.
      [1913 Webster]

   By no means, or By no manner of means, not at all;
      certainly not; not in any degree.
      [1913 Webster]

            The wine on this side of the lake is by no means so
            good as that on the other.            --Addison.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

By \By\ (b[imac]), prep. [OE. bi, AS. b[imac], big, near to, by,
   of, from, after, according to; akin to OS. & OFries. bi, be,
   D. bij, OHG. b[imac], G. bei, Goth. bi, and perh. Gr. 'amfi`.
   E. prefix be- is orig. the same word. [root]203. See pref.
   Be-.]
   1. In the neighborhood of; near or next to; not far from;
      close to; along with; as, come and sit by me.
      [1913 Webster]

            By foundation or by shady rivulet
            He sought them both.                  --Milton.
      [1913 Webster]

   2. On; along; in traversing. Compare 5.
      [1913 Webster]

            Long labors both by sea and land he bore. --Dryden.
      [1913 Webster]

            By land, by water, they renew the charge. --Pope.
      [1913 Webster]

   3. Near to, while passing; hence, from one to the other side
      of; past; as, to go by a church.
      [1913 Webster]

   4. Used in specifying adjacent dimensions; as, a cabin twenty
      feet by forty.
      [1913 Webster]

   5. Against. [Obs.] --Tyndale [1. Cor. iv. 4].
      [1913 Webster]

   6. With, as means, way, process, etc.; through means of; with
      aid of; through; through the act or agency of; as, a city
      is destroyed by fire; profit is made by commerce; to take
      by force.
      [1913 Webster]

   Note: To the meaning of by, as denoting means or agency,
         belong, more or less closely, most of the following
         uses of the word:
      (a) It points out the author and producer; as, "Waverley",
          a novel by Sir W.Scott; a statue by Canova; a sonata
          by Beethoven.
      (b) In an oath or adjuration, it indicates the being or
          thing appealed to as sanction; as, I affirm to you by
          all that is sacred; he swears by his faith as a
          Christian; no, by Heaven.
      (c) According to; by direction, authority, or example of;
          after; -- in such phrases as, it appears by his
          account; ten o'clock by my watch; to live by rule; a
          model to build by.
      (d) At the rate of; according to the ratio or proportion
          of; in the measure or quantity of; as, to sell cloth
          by the yard, milk by the quart, eggs by the dozen,
          meat by the pound; to board by the year.
      (e) In comparison, it denotes the measure of excess or
          deficiency; when anything is increased or diminished,
          it indicates the measure of increase or diminution;
          as, larger by a half; older by five years; to lessen
          by a third.
      (f) It expresses continuance or duration; during the
          course of; within the period of; as, by day, by night.
      (g) As soon as; not later than; near or at; -- used in
          expressions of time; as, by this time the sun had
          risen; he will be here by two o'clock.
          [1913 Webster]

   Note: In boxing the compass, by indicates a pint nearer to,
         or towards, the next cardinal point; as, north by east,
         i.e., a point towards the east from the north;
         northeast by east, i.e., on point nearer the east than
         northeast is.
         [1913 Webster]

   Note: With is used instead of by before the instrument with
         which anything is done; as, to beat one with a stick;
         the board was fastened by the carpenter with nails. But
         there are many words which may be regarded as means or
         processes, or, figuratively, as instruments; and
         whether with or by shall be used with them is a matter
         of arbitrary, and often, of unsettled usage; as, to a
         reduce a town by famine; to consume stubble with fire;
         he gained his purpose by flattery; he entertained them
         with a story; he distressed us with or by a recital of
         his sufferings. see With.
         [1913 Webster]

   By all means, most assuredly; without fail; certainly.

   By and by.
      (a) Close together (of place). [Obs.] "Two yonge knightes
          liggyng [lying] by and by." --Chaucer.
      (b) Immediately; at once. [Obs.] "When . . . persecution
          ariseth because of the word, by and by he is
          offended." --Matt. xiii. 21.
      (c) Presently; pretty soon; before long.

   Note: In this phrase, by seems to be used in the sense of
         nearness in time, and to be repeated for the sake of
         emphasis, and thus to be equivalent to "soon, and
         soon," that is instantly; hence, -- less emphatically,
         -- pretty soon, presently.

   By one's self, with only one's self near; alone; solitary.

   By the bye. See under Bye.

   By the head (Naut.), having the bows lower than the stern;
      -- said of a vessel when her head is lower in the water
      than her stern. If her stern is lower, she is by the
      stern.

   By the lee, the situation of a vessel, going free, when she
      has fallen off so much as to bring the wind round her
      stern, and to take her sails aback on the other side.

   By the run, to let go by the run, to let go altogether,
      instead of slacking off.

   By the way, by the bye; -- used to introduce an incidental
      or secondary remark or subject.

   Day by day, One by one, Piece by piece, etc., each day,
      each one, each piece, etc., by itself singly or
      separately; each severally.

   To come by, to get possession of; to obtain.

   To do by, to treat, to behave toward.

   To set by, to value, to esteem.

   To stand by, to aid, to support.
      [1913 Webster]

   Note: The common phrase good-by is equivalent to farewell,
         and would be better written good-bye, as it is a
         corruption of God be with you (b'w'ye).
         [1913 Webster]

WordNet (r) 3.0 (2006):

by all means
    adv 1: definitely or certainly; "Visit us by all means" [ant:
           by no means, not by a blame sight, not by a long
           sight]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "by all means":
   OK, Roger, absolutely, all right, alright, alrighty, amen,
   and no mistake, as you say, assuredly, at all events, at any rate,
   aye, certainly, clearly, da, decidedly, decisively, definitely,
   distinctly, exactly, fine, for a certainty, for a fact,
   for certain, for sure, forsooth, good, good enough, hear, in truth,
   indeed, indeedy, ja, just so, mais oui, most assuredly,
   most certainly, naturally, naturellement, nothing else but,
   of course, okay, oui, positively, precisely, quite, rather, really,
   right, righto, sure, sure thing, surely, to a certainty,
   to be sure, truly, unequivocally, unmistakably, very well,
   well and good, why yes, yea, yeah, yep, yes, yes indeed,
   yes indeedy, yes sir, yes sirree