1. (a.) Pertaining to, or near, the horizon.

2. (a.) Parallel to the horizon; on a level; as, a horizontal line or surface.

3. (a.) Measured or contained in a plane of the horizon; as, horizontal distance.

arrowlike billiard table bowling green dead flat dead level dead straight direct earth esplanade even flat flatland flattened floor flush ground homaloid homaloidal horizontal axis horizontal fault horizontal line horizontal parallax horizontal plane horizontal projection in a line ledge level level line level plane lineal linear mean sea level parterre plain plane platform prairie prone rectilineal rectilinear right rolled ruler-straight sea level sea of grass smooth smoothed out smoothened squashed squashed flat steppe straight straight-cut straight-front straight-side streamlined supine table tabloid tabular terrace trodden trodden flat TRUE unbending unbent unbowed unbroken uncurved undeflected undeviating undistorted uninterrupted unswerving unturned upright vertical water level