Noah Webster's New International Dictionary of the English Language

1. (a.) Perpendicular to the plane of the horizon; upright; plumb; as, a vertical line.

2. (a.) of or pertaining to the vertex; situated at the vertex, or highest point; directly overhead, or in the zenith; perpendicularly above one.

3. (n.) Vertical position; zenith.

4. (n.) A vertical line, plane, or circle.