A "sack dress" is a loose-fitting dress with no cinching or shaping, resembling a shapeless bag or sack. It is meant to be comfortable and easy to wear without hugging the body. Full definition
I mean, there will never be a potato sack dress that I won't, even just briefly, consider buying. (bluecollarredlipstick.com)
Potato sack dresses are not the height of style, especially when they're a size or two too big, but comfort is also never overrated in my books. (bluecollarredlipstick.com)
In the fall of 2013, juniors in the Fashion Department at Pratt were introduced to Isamu Noguchi's collaborations with the avant - garde dancer / choreographer Ruth Page, for whom he created two royal blue, wool jersey sack dresses in 1932 to pose and dance in: wearable artworks that transformed her into a piece of kinetic sculpture. (noguchi.org)