默默無聞 [－－无闻]

Jyutping mak6 mak6 mou4 man4
Pinyin mò mò wú wén

Definitions (CC-CEDICT)
  1. obscure and unknown (idiom); an outsider without any reputation
  2. a nobody
  3. an unknown quantity
Definitions (粵典–words.hk)
  1. 形容詞
    冇​名​氣​嘅​；​冇​人​識​嘅
    unknown to the public