big word
noun [ C ] informal uk/ˌbɪɡ ˈwɜːd/ us/ˌbɪɡ ˈwɝːd/
大词;又长又艰深的词汇;表达严肃或重要概念的字眼
a long, difficult word, or a word that expresses a serious or important idea
He tried to impress his teachers by using big words in all his essays. 他在所有的作文中，都试图用大词来给老师留下好印象。