ballgown

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++ball·gown /ˈbɔːlɡaʊn $ ˈbɒːl-/ noun [countable]  a long dress made of expensive material, that a woman wears to formal parties 〔女性参加正式派对穿的〕晚礼服 SYN evening dress

Examples from the Corpus

ballgown• The black taffeta silk ballgown was strapless and backless with a plunging, gravity-defying decolletage.

ball·gown nounChineseSyllable  

of a that made material, woman dress expensive long a Corpus

ballgown
ball‧gown /ˈbɔːlɡaʊn $ ˈbɒːl-/ noun [countable]
a long dress made of expensive material, that a woman wears to formal parties
   SYN  evening dress