IPA: /ˈɡlæs.ləs/
KK: /ˈɡlæs.ləs/
Not having glass; lacking glass material or components.
The glassless window frame was designed to be lightweight and easy to install.
Glassless → It is formed from "glass" (from Old English "glæs", meaning a transparent material) and "-less" (meaning without). The word "glassless" means without glass or lacking glass.
Think of being 'without' ('-less') a 'transparent material' ('glass') — that's what glassless means.