near light speed; sublight speed
Technical term used in physics and science fiction to describe speeds close to, but below, the speed of light.
Designs for spacecraft capable of traveling at near light speed are being researched.
Sublight travel often appears in science fiction novels.
Compound of 亜 (a, 'sub-') + 光速 (kōsoku, 'speed of light'). The prefix 亜 indicates something just below or approaching the following concept.