(1):

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

(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):

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

(4):

(n.) Vertical position; zenith.