The Collaborative International Dictionary of English v.0.48:

Horizon \Ho*ri"zon\, n. [F., fr. L. horizon, fr. Gr. ? (sc. ?)
   the bounding line, horizon, fr. ? to bound, fr. ? boundary,
   limit.]
   1. The line which bounds that part of the earth's surface
      visible to a spectator from a given point; the apparent
      junction of the earth and sky.
      [1913 Webster]

            And when the morning sun shall raise his car
            Above the border of this horizon.     --Shak.
      [1913 Webster]

            All the horizon round
            Invested with bright rays.            --Milton.
      [1913 Webster]

   2. (Astron.)
      (a) A plane passing through the eye of the spectator and
          at right angles to the vertical at a given place; a
          plane tangent to the earth's surface at that place;
          called distinctively the sensible horizon.
      (b) A plane parallel to the sensible horizon of a place,
          and passing through the earth's center; -- called also
          rational horizon or celestial horizon.
      (c) (Naut.) The unbroken line separating sky and water, as
          seen by an eye at a given elevation, no land being
          visible.
          [1913 Webster]

   3. (Geol.) The epoch or time during which a deposit was made.
      [1913 Webster]

            The strata all over the earth, which were formed at
            the same time, are said to belong to the same
            geological horizon.                   --Le Conte.
      [1913 Webster]

   4. (Painting) The chief horizontal line in a picture of any
      sort, which determines in the picture the height of the
      eye of the spectator; in an extended landscape, the
      representation of the natural horizon corresponds with
      this line.
      [1913 Webster]

   5. The limit of a person's range of perception, capabilities,
      or experience; as, children raised in the inner city have
      limited horizons.
      [PJC]

   6. [fig.] A boundary point or line, or a time point, beyond
      which new knowledge or experiences may be found; as, more
      powerful computers are just over the horizon.
      [PJC]

   Apparent horizon. See under Apparent.

   Artificial horizon, a level mirror, as the surface of
      mercury in a shallow vessel, or a plane reflector adjusted
      to the true level artificially; -- used chiefly with the
      sextant for observing the double altitude of a celestial
      body.

   Celestial horizon. (Astron.) See def. 2, above.

   Dip of the horizon (Astron.), the vertical angle between
      the sensible horizon and a line to the visible horizon,
      the latter always being below the former.

   Rational horizon, and Sensible horizon. (Astron.) See
      def. 2, above.

   Visible horizon. See definitions 1 and 2, above.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dip \Dip\, n.
   1. The action of dipping or plunging for a moment into a
      liquid. "The dip of oars in unison." --Glover.
      [1913 Webster]

   2. Inclination downward; direction below a horizontal line;
      slope; pitch.
      [1913 Webster]

   3. a hollow or depression in a surface, especially in the
      ground.
      [PJC]

   4. A liquid, as a sauce or gravy, served at table with a
      ladle or spoon. [Local, U.S.] --Bartlett.
      [1913 Webster]

   5. A dipped candle. [Colloq.] --Marryat.
      [1913 Webster]

   6. A gymnastic exercise on the parallel bars in which the
      performer, resting on his hands, lets his arms bend and
      his body sink until his chin is level with the bars, and
      then raises himself by straightening his arms.
      [Webster 1913 Suppl.]

   7. In the turpentine industry, the viscid exudation, which is
      dipped out from incisions in the trees; as, virgin dip
      (the runnings of the first year), yellow dip (the runnings
      of subsequent years).
      [Webster 1913 Suppl.]

   8. (A["e]ronautics) A sudden drop followed by a climb,
      usually to avoid obstacles or as the result of getting
      into an airhole.
      [Webster 1913 Suppl.]

   9. a liquid, in which objects are soaked by dipping; e.g., a
      parasiticide or insecticide solution into which animals
      are dipped (see sheep-dip).
      [PJC]

   10. a sauce into which foods are dipped to enhance the
       flavor; e. g., an onion dip made from sour cream and
       dried onions, into which potato chips are dipped.
       [PJC]

   11. a pickpocket. [slang]
       [PJC]

   Dip of the horizon (Astron.), the angular depression of the
      seen or visible horizon below the true or natural horizon;
      the angle at the eye of an observer between a horizontal
      line and a tangent drawn from the eye to the surface of
      the ocean.

   Dip of the needle, or Magnetic dip, the angle formed, in
      a vertical plane, by a freely suspended magnetic needle,
      or the line of magnetic force, with a horizontal line; --
      called also inclination.

   Dip of a stratum (Geol.), its greatest angle of inclination
      to the horizon, or that of a line perpendicular to its
      direction or strike; -- called also the pitch.
      [1913 Webster]