horizontal
horizontal (hôrĭ-zŏnʹtl, hŏr-) adjective
Abbr. hor.
1. Of, relating to, or near the horizon.
2. a. Parallel to or in the plane of the horizon. b. At right angles to a vertical line.
3. Occupying or restricted to the same level in a hierarchy: a horizontal study of verbal ability; a horizontal transfer for an employee.
noun
Something, such as a line, a plane, or an object, that is horizontal.
[French, from Latin horizōn, horizont-, horizon. See horizon.]
horizonʹtally adverb