Source : Webster's Revised Unabridged Dictionary (1913)

Rule \Rule\, n. [OE. reule, riule, OF. riule, reule, F.
   r['e]gle, fr. L. regula a ruler, rule, model, fr. regere,
   rectum, to lead straight, to direct. See {Right}, a., and cf.
   {Regular}.]
   1. That which is prescribed or laid down as a guide for
      conduct or action; a governing direction for a specific
      purpose; an authoritative enactment; a regulation; a
      prescription; a precept; as, the rules of various
      societies; the rules governing a school; a rule of
      etiquette or propriety; the rules of cricket.

            We profess to have embraced a religion which
            contains the most exact rules for the government of
            our lives.                            --Tillotson.

   2. Hence:
      (a) Uniform or established course of things.

                'T is against the rule of nature. --Shak.
      (b) Systematic method or practice; as, my ule is to rise
          at six o'clock.
      (c) Ordibary course of procedure; usual way; comon state
          or condition of things; as, it is a rule to which
          there are many exeptions.
      (d) Conduct in general; behavior. [Obs.]

                This uncivil rule; she shall know of it. --Shak.

   3. The act of ruling; administration of law; government;
      empire; authority; control.

            Obey them that have the rule over you. --Heb. xiii.
                                                  17.

            His stern rule the groaning land obeyed. --Pope.

   4. (Law) An order regulating the practice of the courts, or
      an order made between parties to an action or a suit.
      --Wharton.

   5. (Math.) A determinate method prescribed for performing any
      operation and producing a certain result; as, a rule for
      extracting the cube root.

   6. (Gram.) A general principle concerning the formation or
      use of words, or a concise statement thereof; thus, it is
      a rule in England, that s or es, added to a noun in the
      singular number, forms the plural of that noun; but
      ``man'' forms its plural ``men'', and is an exception to
      the rule.

   7.
      (a) A straight strip of wood, metal, or the like, which
          serves as a guide in drawing a straight line; a ruler.
      (b) A measuring instrument consisting of a graduated bar
          of wood, ivory, metal, or the like, which is usually
          marked so as to show inches and fractions of an inch,
          and jointed so that it may be folded compactly.

                A judicious artist will use his eye, but he will
                trust only to his rule.           --South.

   8. (Print.)
      (a) A thin plate of metal (usually brass) of the same
          height as the type, and used for printing lines, as
          between columns on the same page, or in tabular work.
      (b) A composing rule. See under {Conposing}.

   {As a rule}, as a general thing; in the main; usually; as, he
      behaves well, as a rule.

   {Board rule}, {Caliber rule}, etc. See under {Board},
      {Caliber}, etc.

   {Rule joint}, a knuckle joint having shoulders that abut when
      the connected pieces come in line with each other, and
      thus permit folding in one direction only.

   {Rule of three} (Arith.), that rule which directs, when three
      terms are given, how to find a fourth, which shall have
      the same ratio to the third term as the second has to the
      first; proportion. See {Proportion}, 5
      (b) .

   {Rule of thumb}, any rude process or operation, like that of
      using the thumb as a rule in measuring; hence, judgment
      and practical experience as distinguished from scientific
      knowledge.

   Syn: regulation; law; precept; maxim; guide; canon; order;
        method; direction; control; government; sway; empire.

Board \Board\, n. [OE. bord, AS. bord board, shipboard; akin to
   bred plank, Icel. bor? board, side of a ship, Goth.
   f?tu-baurd]/> footstool, D. bord board, G. brett, bort. See
   def. 8. [root]92.]
   1. A piece of timber sawed thin, and of considerable length
      and breadth as compared with the thickness, -- used for
      building, etc.

   Note: When sawed thick, as over one and a half or two inches,
         it is usually called a plank.

   2. A table to put food upon.

   Note: The term board answers to the modern table, but it was
         often movable, and placed on trestles. --Halliwell.

               Fruit of all kinds . . . She gathers, tribute
               large, and on the board Heaps with unsparing
               hand.                              --Milton.

   3. Hence: What is served on a table as food; stated meals;
      provision; entertainment; -- usually as furnished for pay;
      as, to work for one's board; the price of board.

   4. A table at which a council or court is held. Hence: A
      council, convened for business, or any authorized assembly
      or meeting, public or private; a number of persons
      appointed or elected to sit in council for the management
      or direction of some public or private business or trust;
      as, the Board of Admiralty; a board of trade; a board of
      directors, trustees, commissioners, etc.

            Both better acquainted with affairs than any other
            who sat then at that board.           --Clarendon.

            We may judge from their letters to the board.
                                                  --Porteus.

   5. A square or oblong piece of thin wood or other material
      used for some special purpose, as, a molding board; a
      board or surface painted or arranged for a game; as, a
      chessboard; a backgammon board.

   6. Paper made thick and stiff like a board, for book covers,
      etc.; pasteboard; as, to bind a book in boards.

   7. pl. The stage in a theater; as, to go upon the boards, to
      enter upon the theatrical profession.

   8. [In this use originally perh. a different word meaning
      border, margin; cf. D. boord, G. bord, shipboard, and G.
      borte trimming; also F. bord (fr. G.) the side of a ship.
      Cf. {Border}.] The border or side of anything. (Naut.)
      (a) The side of a ship. ``Now board to board the rival
          vessels row.'' --Dryden. See {On board}, below.
      (b) The stretch which a ship makes in one tack.

   Note: Board is much used adjectively or as the last part of a
         compound; as, fir board, clapboard, floor board,
         shipboard, sideboard, ironing board, chessboard,
         cardboard, pasteboard, seaboard; board measure.

   {The American Board}, a shortened form of ``The American
      Board of Commissioners for Foreign Missions'' (the foreign
      missionary society of the American Congregational
      churches).

   {Bed and board}. See under {Bed}.

   {Board and board} (Naut.), side by side.

   {Board of control}, six privy councilors formerly appointed
      to superintend the affairs of the British East Indies.
      --Stormonth.

   {Board rule}, a figured scale for finding without calculation
      the number of square feet in a board. --Haldeman.

   {Board of trade}, in England, a committee of the privy
      council appointed to superintend matters relating to
      trade. In the United States, a body of men appointed for
      the advancement and protection of their business
      interests; a chamber of commerce.

   {Board wages}.
      (a) Food and lodging supplied as compensation for
          services; as, to work hard, and get only board wages.
      (b) Money wages which are barely sufficient to buy food
          and lodging.
      (c) A separate or special allowance of wages for the
          procurement of food, or food and lodging. --Dryden.

   {By the board}, over the board, or side. ``The mast went by
      the board.'' --Totten. Hence (Fig.),

   {To go by the board}, to suffer complete destruction or
      overthrow.

   {To enter on the boards}, to have one's name inscribed on a
      board or tablet in a college as a student. [Cambridge,
      England.] ``Having been entered on the boards of Trinity
      college.'' --Hallam.

   {To make a good board} (Naut.), to sail in a straight line
      when close-hauled; to lose little to leeward.

   {To make short boards}, to tack frequently.

   {On board}.
      (a) On shipboard; in a ship or a boat; on board of; as, I
          came on board early; to be on board ship.
      (b) In or into a railway car or train. [Colloq. U. S.]

   {Returning board}, a board empowered to canvass and make an
      official statement of the votes cast at an election.
      [U.S.]

Source : WordNet®

board rule
     n : a measure used in computing board feet