horizontally

adjective

1. of or near the horizon
2. 1. parallel to the plane of the horizon; not vertical
   2. placed, operating, or acting chiefly in a horizontal direction
3. flat and even; level
4. at, or made up of elements at, the same levels of industrial production and distribution, or of status

Origin: ModL horizontalis < L horizon (gen. horizontis): see horizon

noun

1. a horizontal line, plane, etc.
2. position parallel to the horizon