Examples from the Web for horizontally
Faulkner, Whitman, and Dickinson did not labor in vain; their books live on, horizontally, stacked like bricks in a display case.A Teacher Returns to the Classroom and Gets Schooled|Nick Romeo|September 1, 2014|DAILY BEAST
Johns took the original source and mirrored it horizontally, creating a large missing void in the center of the work.
Thigh-high leather boots… Gucci ostrich skin leather jackets… Horizontally striped posing briefs… More leather jackets...
According to one publicist, the answer lies in branching out into a "horizontally integrated economic model."
She was walking down the stairs of East High School in a pair of horizontally striped bell bottoms.
Horizontally, the head and body traverse an arc of about 100°; vertically, they traverse an arc slightly less than 180°.Natural History of the Bell Vireo, Vireo bellii Audubon|Jon C. Barlow
But for all three to be horizontally in the same straight line is quite another matter.The Story of the Solar System|George F. Chambers
Take two slats and place one under one oblong and over the other, horizontally.Home Occupations for Boys and Girls|Bertha Johnston
The Salmon-leap—lying flat on his face and then springing up, horizontally, high in the air.
The stitch is taken vertically instead of horizontally, as in cat-stitch.The Library of Work and Play: Needlecraft|Effie Archer Archer
British Dictionary definitions for horizontally
Word Origin and History for horizontally
1550s, "relating to or near the horizon," from French horizontal, from Latin horizontem (see horizon). Meaning "flat" (i.e., "parallel to the horizon") is from 1630s. Related: horizontally.