IPA: /ˈstɑːrləs/
KK: /ˈstɑr.ləs/
Not having any visible stars in the sky.
On a starless night, the sky appeared completely dark.
Starless → It is formed from "star" (from Old English *steorra*, meaning a celestial body that shines in the night sky) and "-less" (meaning without). The word "starless" means without stars or lacking stars in the sky.
Imagine a night sky that is 'without' ('-less') any 'stars' — that's what 'starless' means.