1 Three Gorges on the Chang Jiang or Yangtze, namely: Qutang Gorge 瞿塘峽|瞿塘峡[Qú táng Xiá], Wuxia Gorge 巫峽|巫峡[Wū Xiá] and Xiling Gorge 西陵峽|西陵峡[Xī líng Xiá]
2 Sanxia or Sanhsia town in New Taipei City 新北市[Xīn běi shì], Taiwan
1 lit. to reply "don't know" whatever the question (idiom)
2 fig. absolutely no idea of what's going on
3 complete ignorance
一日三秋
yī rì sān qiū
1 a single day apart seems like three seasons (idiom)
一日不见，如隔三秋
yī rì bù jiàn , rú gé sān qiū
1 one day apart seems like three years (idiom)
一板三眼
yī bǎn sān yǎn
1 lit. one strong beat and three weak beats in a measure of music (four beats in the bar) (idiom); fig. scrupulous attention to detail
三七二十一
sān qī èr shí yī
1 three sevens are twenty-one (idiom)
2 the facts of the matter
3 the actual situation
三下两下
sān xià liǎng xià
1 quickly and effortlessly (idiom)
三五成群
sān wǔ chéng qún
1 in groups of three or four (idiom)
三人成虎
sān rén chéng hǔ
1 three men talking makes a tiger (idiom); repeated rumor becomes a fact
三人行，必有我师
sān rén xíng , bì yǒu wǒ shī
1 lit. if three walk together, one can be my teacher (idiom, from the Analects of Confucius)
2 you have sth to learn from everyone
三令五申
sān lìng wǔ shēn
1 to order again and again (idiom)
三个和尚没水喝
sān gè hé shang méi shuǐ hē
1 lit. three monks have no water to drink (idiom)
2 fig. everybody's business is nobody's business
3 (If there is one monk, he will fetch water for himself. If there are two, they will fetch water together. But if there are three or more, none will take it upon himself to fetch water.)