Wiktionary
subluminous
a. (context astronomy English) Describing a star that is fainter than main sequence stars of the same colour
Usage examples of "subluminous".
On the right, the sun was slowly sinking behind the ancient trees of the Kuntsevo park--one half of its brilliant disc obscured with grey, subluminous cloud, and the other half sending forth spokes of flaming light which threw the old trees into striking relief as they stood there with their dense crowns of green showing against a blue patch of sky.