Dip of a stratum

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]