IPA: /ˈstrɛtʃiər/
KK: /ˈstrɛtʃiər/
More capable of being stretched than something else.
This fabric is stretchier than the one we used before.
Stretchier → It is formed from "stretch" (from Old English *streccan*, meaning to extend or draw out) and the suffix "-ier" (indicating a comparative form). The word "stretchier" means more capable of being extended or drawn out than something else.
Think of something that can be 'extended' or 'drawn out' more than another — that's what 'stretchier' means.