neckline

noun

1. the opening at the neck of a garment, especially of a woman’s garment, with reference to its shape or its position on the body: a V-neckline; a high neckline.

noun

1. the shape or position of the upper edge of a dress, blouse, etca plunging neckline

n.also neck-line, of a garment, 1900, from neck (n.) + line (n.).