IPA: /ˈʃeɪpləsli/
KK: /ˈʃeɪpləsli/
In a way that lacks a definite shape or form.
The clouds floated shapelessly across the sky.
Shapelessly → It is formed from "shape" (from Old English *sceap*, meaning form or appearance) and "-less" (meaning without) and "-ly" (meaning in a manner). The word "shapelessly" means in a manner that is without form or shape.
Think of being 'without' ('-less') a 'form' ('shape') — that's why shapelessly means lacking shape.