理屈词穷

理屈詞窮
qióng
  1. lit. having presented a flawed argument, one has nothing further to add (idiom)
  2. fig. unable to provide a convincing argument to support one's position
  3. to not have a leg to stand on

CEDICT

to be unable to put forth any convincing arguments to justify one's opinion; to not have a leg to stand on

Wiktionary

由于理亏反驳得无。《红楼梦第一》:「理屈词穷从此好好用功。」词穷理屈」。

重編國語辭典

由于理亏反驳得无

維基詞典

Entry Composition