Source : Webster's Revised Unabridged Dictionary (1913)

Vertical \Ver"ti*cal\, a. [Cf. F. vertical. See {Vertex}.]
   1. Of or pertaining to the vertex; situated at the vertex, or
      highest point; directly overhead, or in the zenith;
      perpendicularly above one.

            Charity . . . is the vertical top of all religion.
                                                  --Jer. Taylor.

   2. Perpendicular to the plane of the horizon; upright; plumb;
      as, a vertical line.

   {Vertical angle} (Astron. & Geod.), an angle measured on a
      vertical circle, called an angle of elevation, or
      altitude, when reckoned from the horizon upward, and of
      depression when downward below the horizon.

   {Vertical anthers} (Bot.), such anthers as stand erect at the
      top of the filaments.

   {Vertical circle} (Astron.), an azimuth circle. See under
      {Azimuth}.

   {Vertical drill}, an drill. See under {Upright}.

   {Vertical fire} (Mil.), the fire, as of mortars, at high
      angles of elevation.

   {Vertical leaves} (Bot.), leaves which present their edges to
      the earth and the sky, and their faces to the horizon, as
      in the Australian species of Eucalyptus.

   {Vertical limb}, a graduated arc attached to an instrument,
      as a theodolite, for measuring vertical angles.

   {Vertical line}.
      (a) (Dialing) A line perpendicular to the horizon.
      (b) (Conic Sections) A right line drawn on the vertical
          plane, and passing through the vertex of the cone.
      (c) (Surv.) The direction of a plumb line; a line normal
          to the surface of still water.
      (d) (Geom., Drawing, etc.) A line parallel to the sides of
          a page or sheet, in distinction from a horizontal line
          parallel to the top or bottom.

   {Vertical plane}.
      (a) (Conic Sections) A plane passing through the vertex of
          a cone, and through its axis.
      (b) (Projections) Any plane which passes through a
          vertical line.
      (c) (Persp.) The plane passing through the point of sight,
          and perpendicular to the ground plane, and also to the
          picture.

   {Vertical sash}, a sash sliding up and down. Cf. {French
      sash}, under 3d {Sash}.

   {Vertical steam engine}, a steam engine having the crank
      shaft vertically above or below a vertical cylinder.

Source : WordNet®

vertical angle
     n : either of two equal and opposite angles formed by the
         intersection of two straight lines