perfect vacuum; absolute vacuum
Technical term in physics and engineering for a space entirely devoid of matter, or a vacuum of the highest attainable quality.
Creating a perfect vacuum is nearly impossible in theory.
This experiment requires an environment close to an absolute vacuum.
真空 is the general term for 'vacuum', while 絶対真空 specifically emphasizes a theoretically perfect or absolute vacuum.
Compound of 絶対 (absolute) and 真空 (vacuum). The exact historical derivation is uncertain; the term is a modern technical coinage.