泥牛入海 [－－－－]

Jyutping nai4 ngau4 jap6 hoi2
Pinyin ní niú rù hǎi

Definitions (CC-CEDICT)
  1. lit. a clay ox enters the sea (idiom); fig. to disappear with no hope of returning
Definitions (Wiktionary)
  1. phrase, idiomatic
    gone forever and without a trace