Source : Webster's Revised Unabridged Dictionary (1913)

Grain \Grain\, n. [F. grain, L. granum, grain, seed, small
   kernel, small particle. See {Corn}, and cf. {Garner}, n.,
   {Garnet}, {Gram} the chick-pea, {Granule}, {Kernel.}]
   1. A single small hard seed; a kernel, especially of those
      plants, like wheat, whose seeds are used for food.

   2. The fruit of certain grasses which furnish the chief food
      of man, as corn, wheat, rye, oats, etc., or the plants
      themselves; -- used collectively.

            Storehouses crammed with grain.       --Shak.

   3. Any small, hard particle, as of sand, sugar, salt, etc.;
      hence, any minute portion or particle; as, a grain of
      gunpowder, of pollen, of starch, of sense, of wit, etc.

            I . . . with a grain of manhood well resolved.
                                                  --Milton.

   4. The unit of the English system of weights; -- so called
      because considered equal to the average of grains taken
      from the middle of the ears of wheat. 7,000 grains
      constitute the pound avoirdupois, and 5,760 grains the
      pound troy. A grain is equal to .0648 gram. See {Gram.}

   5. A reddish dye made from the coccus insect, or kermes;
      hence, a red color of any tint or hue, as crimson,
      scarlet, etc.; sometimes used by the poets as equivalent
      to {Tyrian purple}.

            All in a robe of darkest grain.       --Milton.

            Doing as the dyers do, who, having first dipped
            their silks in colors of less value, then give' them
            the last tincture of crimson in grain. --Quoted by
                                                  Coleridge,
                                                  preface to
                                                  Aids to
                                                  Reflection.

   6. The composite particles of any substance; that arrangement
      of the particles of any body which determines its
      comparative roughness or hardness; texture; as, marble,
      sugar, sandstone, etc., of fine grain.

            Hard box, and linden of a softer grain. --Dryden.

   7. The direction, arrangement, or appearance of the fibers in
      wood, or of the strata in stone, slate, etc.

            Knots, by the conflux of meeting sap, Infect the
            sound pine and divert his grain Tortive and errant
            from his course of growth.            --Shak.

   8. The fiber which forms the substance of wood or of any
      fibrous material.

   9. The hair side of a piece of leather, or the marking on
      that side. --Knight.

   10. pl. The remains of grain, etc., after brewing or
       distillation; hence, any residuum. Also called {draff.}

   11. (Bot.) A rounded prominence on the back of a sepal, as in
       the common dock. See {Grained}, a., 4.

   12. Temper; natural disposition; inclination. [Obs.]

             Brothers . . . not united in grain.  --Hayward.

   13. A sort of spice, the grain of paradise. [Obs.]

             He cheweth grain and licorice, To smellen sweet.
                                                  --Chaucer.

   {Against the grain}, against or across the direction of the
      fibers; hence, against one's wishes or tastes;
      unwillingly; unpleasantly; reluctantly; with difficulty.
      --Swift.--Saintsbury.

   {A grain of allowance}, a slight indulgence or latitude a
      small allowance.

   {Grain binder}, an attachment to a harvester for binding the
      grain into sheaves.

   {Grain colors}, dyes made from the coccus or kermes in sect.
      

   {Grain leather}.
       (a) Dressed horse hides.
       (b) Goat, seal, and other skins blacked on the grain side
           for women's shoes, etc.

   {Grain moth} (Zo["o]l.), one of several small moths, of the
      family {Tineid[ae]} (as {Tinea granella} and {Butalis
      cerealella}), whose larv[ae] devour grain in storehouses.
      

   {Grain side} (Leather), the side of a skin or hide from which
      the hair has been removed; -- opposed to {flesh side.}

   {Grains of paradise}, the seeds of a species of amomum.

   {grain tin}, crystalline tin ore metallic tin smelted with
      charcoal.

   {Grain weevil} (Zo["o]l.), a small red weevil (Sitophilus
      granarius), which destroys stored wheat and othar grain,
      by eating out the interior.

   {Grain worm} (Zo["o]l.), the larva of the grain moth. See
      {grain moth}, above.

   {In grain}, of a fast color; deeply seated; fixed; innate;
      genuine. ``Anguish in grain.'' --Herbert.

   {To dye in grain}, to dye of a fast color by means of the
      coccus or kermes grain [see {Grain}, n., 5]; hence, to dye
      firmly; also, to dye in the wool, or in the raw material.
      See under {Dye.}

            The red roses flush up in her cheeks . . . Likce
            crimson dyed in grain.                --Spenser.

   {To go against the grain of} (a person), to be repugnant to;
      to vex, irritate, mortify, or trouble.

Source : WordNet®

grain moth
     n : moth whose larvae feed on grain