noun
vertical plane
Technical term used in geometry, engineering, and related fields to refer to a plane perpendicular to the horizontal plane.
この図では、鉛直面に投影された形状を示している。
This diagram shows the shape projected onto a vertical plane.
水平面 means 'horizontal plane', the counterpart to 鉛直面.
Compound of 鉛直 (vertical) + 面 (plane). 鉛直 originally referred to the direction of a plumb line.