grunt

1. (of an animal, especially a pig) make a low, short guttural sound.

   an enormous pig grunted and shuffled in a sty outside

1. a low, short guttural sound made by an animal or a person.

   with snorts and grunts the animals were coaxed down the ramp

   he answered with a grunt and made no further reply

2. a low-ranking soldier or unskilled worker.

   he went from grunt to senior executive vice president in five years

3. mechanical power, especially in a motor vehicle.

   what the big wagon needs is grunt, and the turbo does the business

4. an edible shoaling fish of tropical coasts and coral reefs, able to make a loud noise by grinding its teeth and amplifying the sound in the swim bladder.

Old English grunnettan, of Germanic origin and related to German grunzen ; probably originally imitative.