hor·i·zon·tal .hȯr-ə-'zänt-əl, .här- adj
1) relating to or being a transverse plane or section of the body
2) relating to or being transmission (as of a disease) by physical contact or proximity in contrast with inheritance compare VERTICAL
hor·i·zon·tal·ly -əl-ē adv
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hor·i·zon·tal (hor″ĭ-zonґtəl) 1. parallel to the plane of the horizon; see also horizontalis. 2. occupying or confined to a single level in a hierarchy; see under transmission.Medical dictionary. 2011.