IPA: /ˈkɒl.ə.ləs/
KK: /ˈkɑːlərləs/
Describing a piece of clothing that does not have a collar.
She wore a collarless shirt to the party.
Collarless → It is formed from "collar" (from Old French *col*, meaning neck) and "-less" (meaning without). The word "collarless" describes something that does not have a collar, particularly in clothing.
Think of a shirt or garment that is 'without' ('-less') a 'neck' ('collar') — that's what collarless means.