grunt

grunt /gr'ʌnt/ (grunts grunting grunted)
1 [VERB] V, V with quote, V n
If you grunt, you make a low sound, especially because you are annoyed or not interested in something.
The driver grunted, convinced that Michael was crazy...
`Rubbish,' I grunted...
He grunted his thanks.
[N-COUNT] oft N of n
Grunt is also a noun.
Their replies were no more than grunts of acknowledgement.
2 [VERB] V
When an animal grunts, it makes a low rough noise.
...the sound of a pig grunting.