IPA: /ˈsæʃləs/
KK: /sæʃləs/
Not having a sash, which is a strip of cloth worn around the waist or over the shoulder.
The dress was sashless, giving it a simple and elegant look.
Sashless → It is formed from "sash" (from Middle English *sash*, meaning a strip of cloth or ribbon) and "-less" (meaning without). The word "sashless" means without a sash or strip of cloth.
Think of being 'without' ('-less') a 'strip of cloth' ('sash') — that's what sashless means.