horizontal

Short definition from Wiktionary

Adjective

1. 1
   Perpendicular to the vertical; parallel to the plane of the horizon; level, flat.
2. 2
   Relating to horizontal markets
3. 3
   Pertaining to the horizon.
4. 4
   Involving wines of the same vintages but from different wineries.
5. 5
   Having the two notes sound successively.
6. 6
   Relating to sexual intercourse.
7. 7
   Being or relating to the transmission of organisms between biotic and/or abiotic members of an ecosystem that are not in a parent-progeny relationship.

Noun

1. 1
   A horizontal component of a structure.
2. 2
   Horizon.
3. 3
   A Tasmanian shrub or small tree whose main trunk tends to lean over and grow horizontally, Anodopetalum biglandulosum