むむ
mumu

Interjection

1. hum; hmm

Onomatopoeia
Interjection

2. hm hm (light chuckle with mouth closed)

Onomatopoeia
Related to ふふ
Interjection

3. uh-huh

Onomatopoeia
Related to うんうん
Interjection

4. mm; hmm

Onomatopoeia
Interjection

5. well

Onomatopoeia