你呢個傳言我真係聞所未聞喎，都唔知信唔信得過。
你呢个传言我真系闻所未闻㖞，都唔知信唔信得过。
nei5 ni1 go3 cyun4 jin4 ngo5 zan1 hai6 man4 so2 mei6 man4 wo3, dou1 m4 zi1 seon3 m4 seon3 dak1 gwo3. I've never heard of that rumour before, I don't know if I should believe it or not.
Definitions (Wiktionary)
phrase, idiomatic
to hear something one has never heard before; (of something) unheard-of, rare
Definitions (Kaifangcidian)
（沒有對應漢語詞彙）
Examples (Tatoeba—Mandarin-English)
Mandarin
日本人太了解本国的事，而对国外的事闻所未闻。韩国人只知道日本的事，而对韩国自己的事一概不知。
日本人太瞭解本國的事，而對國外的事聞所未聞。韓國人只知道日本的事，而對韓國自己的事一概不知。
rì běn rén tài liǎo jiě běn guó de shì ， ér duì guó wài de shì wén suǒ wèi wén 。 hán guó rén zhǐ zhī dào rì běn de shì ， ér duì hán guó zì jǐ de shì yī gài bù zhī 。
The Japanese watch Japan too much and don't know the situation overseas. Koreans watch Japan only and don't know the situation of their own country.