1. A prefix to many terms of art, signifying flat, as Plano-concave, flat on one side and concave on the other. Plano-conical, level on one side and conical on the other. Plano-convex, flat on one side and convex on the other. Plano-horizontal, having a level, horizontal surface or position. Plano-subulate, smooth and awl-shaped.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• planse,
• plainy,
• plaing,
• planon,
• plian,
• pllans,
• rplan,
• plaine,
• plean,
• pleny,
• polans,
• eplane,
• planys,
• plaan,
• pland,
• planni,
• planly,
• planem,
• plana,
• plaqu

• plain,
• plan,
• plane,
• Pliny,
• pleione.

The adjective form of the word "plano" would be "planar".