Merriam-Webster's Collegiate® Dictionary, 11th Edition
GRUNT
I. verb
Etymology: Middle English, from Old English grunnettan, frequentative of grunian, of imitative origin Date: before 12th century intransitive verb to utter a grunt, transitive verb to utter with a grunt, grunter noun
II. noun
Date: 1553
1. the deep short sound characteristic of a hog, a similar sound, any of a family (Haemulidae syn. Pomadasyidae) of chiefly tropical marine bony fishes, a dessert made by dropping biscuit dough on top of boiling berries and steaming ,
4. a United States army or marine foot soldier especially in the Vietnam War, one who does routine unglamorous work