The phrase "square neck" refers to the shape of a neckline on a garment, specifically a square-shaped opening that sits on the shoulders and collarbones. Full definition
Having sleeveless dress with square neck line from tulle and silk will improve your look. (bmodish.com)
It features floor length column silhouette made of one - piece white silky satin that falls straight down from square neck to floor length hem with a draped skirt at under part. (wepromdresses.net)
A sleek black one - piece with a classic fit offers easy poolside style, with a flattering square neck and scoop back. (usa.frenchconnection.com)