Source : Webster's Revised Unabridged Dictionary (1913)

By \By\ (b[imac]), prep. [OE. bi, AS. b[=i], big, near to, by,
   of, from, after, according to; akin to OS. & OFries. bi, be,
   D. bij, OHG. b[=i], 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.

   2. On; along; in traversing. Compare 5.

            Long labors both by sea and land he bore. --Dryden.

            By land, by water, they renew the charge. --Pope.

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

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

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

   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.

   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.

   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.

   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}.

   {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.

   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).



   {Anniversary day}. See {Anniversary}, n.

   {Astronomical day}, a period equal to the mean solar day, but
      beginning at noon instead of at midnight, its twenty-four
      hours being numbered from 1 to 24; also, the sidereal day,
      as that most used by astronomers.

   {Born days}. See under {Born}.

   {Canicular days}. See {Dog day}.

   {Civil day}, the mean solar day, used in the ordinary
      reckoning of time, and among most modern nations beginning
      at mean midnight; its hours are usually numbered in two
      series, each from 1 to 12. This is the period recognized
      by courts as constituting a day. The Babylonians and
      Hindoos began their day at sunrise, the Athenians and Jews
      at sunset, the ancient Egyptians and Romans at midnight.
      

   {Day blindness}. (Med.) See {Nyctalopia}.

   {Day by day}, or {Day after day}, daily; every day;
      continually; without intermission of a day. See under
      {By}. ``Day by day we magnify thee.'' --Book of Common
      Prayer.

   {Days in bank} (Eng. Law), certain stated days for the return
      of writs and the appearance of parties; -- so called
      because originally peculiar to the Court of Common Bench,
      or Bench (bank) as it was formerly termed. --Burrill.

   {Day in court}, a day for the appearance of parties in a
      suit.

   {Days of devotion} (R. C. Ch.), certain festivals on which
      devotion leads the faithful to attend mass. --Shipley.

   {Days of grace}. See {Grace}.

   {Days of obligation} (R. C. Ch.), festival days when it is
      obligatory on the faithful to attend Mass. --Shipley.

   {Day owl}, (Zo["o]l.), an owl that flies by day. See {Hawk
      owl}.

   {Day rule} (Eng. Law), an order of court (now abolished)
      allowing a prisoner, under certain circumstances, to go
      beyond the prison limits for a single day.

   {Day school}, one which the pupils attend only in daytime, in
      distinction from a boarding school.

   {Day sight}. (Med.) See {Hemeralopia}.

   {Day's work} (Naut.), the account or reckoning of a ship's
      course for twenty-four hours, from noon to noon.

   {From day to day}, as time passes; in the course of time; as,
      he improves from day to day.

   {Jewish day}, the time between sunset and sunset.

   {Mean solar day} (Astron.), the mean or average of all the
      apparent solar days of the year.

   {One day}, {One of these days}, at an uncertain time, usually
      of the future, rarely of the past; sooner or later.
      ``Well, niece, I hope to see you one day fitted with a
      husband.'' --Shak.

   {Only from day to day}, without certainty of continuance;
      temporarily. --Bacon.

   {Sidereal day}, the interval between two successive transits
      of the first point of Aries over the same meridian. The
      Sidereal day is 23 h. 56 m. 4.09 s. of mean solar time.

   {To win the day}, to gain the victory, to be successful. --S.
      Butler.

   {Week day}, any day of the week except Sunday; a working day.
      

   {Working day}.
      (a) A day when work may be legally done, in distinction
          from Sundays and legal holidays.
      (b) The number of hours, determined by law or custom,
          during which a workman, hired at a stated price per
          day, must work to be entitled to a day's pay.

Source : WordNet®

day by day
     adv : gradually and progressively; "his health weakened day by
           day" [syn: {daily}]