dé ‧ colle ‧ tage /ˌdeɪkɒlˈtɑːʒ $ deɪˌkɑːləˈtɑːʒ/ BrE AmE noun [uncountable]
[ Date: 1800-1900 ; Language: French ; Origin: collet 'collar' ]
the top edge of a woman’s dress that is cut very low to show part of her shoulders and breasts
—décolleté /deɪˈkɒlteɪ $ ˌdeɪkɑːləˈteɪ/ adjective