言之凿凿

言之鑿鑿
yánzhīzáozáo
(idiom) to speak with conviction

CEDICT

to say with certainty; to speak on good grounds

Wiktionary

说话确实而有根据

維基詞典

Entry Composition

1 言 yán
  1. words
  2. speech
  3. to say
  4. to talk
2 之 zhī
  1. (possessive particle, literary equivalent of 的 de)
  2. him
  3. her
  4. it
3 凿凿 záozáo
  1. (literary) bright; brilliant; vivid
  2. bright; brilliant; vivid
  3. true; real; reliable; credible