むむ

むむmumu

interjection

  1. hum
  2. hmm
  3. hm hm (light chuckle with mouth closed)
  4. uh-huh
  5. mm
  6. well

Study it in Yanamino

Data from JMdict, KANJIDIC2 (EDRDG), KanjiVG, CC-CEDICT and Make Me a Hanzi. Sources and licences