A "loose cardigan" is a type of sweater that is not fitted or tight. It is typically a relaxed and comfortable garment that hangs loosely on the body. Full definition
A simple fix I've used with looser cardigans and dresses is a skinny belt at the smallest part of the waist while leaving the cardi opened underneath. (modernmrsdarcy.com)
Personally, I like wearing loose cardigans in chunky knits or short skirt and long coat paired with suede high boots. (becomechic.com)
V - neck sweater framed with a button and styled with ribbed cuffs and hem; Turtleneck sweater with long sleeves; lace pattern knitted sweaters; woollen one with crisp stripes; Cowl neck and long sleeved pullover; sleeveless cardigan, The Classic loose cardigan in Camel - off, open front geometric pattern cardigan, and sweaters. (stylesgap.com)