:of or relating to the apparent junction of earth and sky :situated near the horizon
:parallel to, in the plane of, or operating in a plane parallel to the horizon or to a baseline :level
:relating to, directed toward, or consisting of individuals or entities of similar status or on the same level
:relating to or being transmission (as of a disease) by physical contact or proximity in contrast with inheritance
— compare vertical 4
- Genes are normally inherited from parents, but they can also be inserted into a genome by viruses, plasmids, and other foreign agents—a phenomenon called horizontal transfer.
- —Stephan Reebs