Grunt, v. t. [imp. & p. p. Grunted; p. pr. & vb. n. Grunting.]
Etymology: [OE. grunten; akin to As. grunian, G. grunzen, Dan. grynte, Sw. grymta; all prob. of imitative; or perh. akin to E. groan.]
To make a deep, short noise, as a hog; to utter a short groan or a deep guttural sound. Who would fardels bear, To grunt and sweat under a weary life. Shak. Grunting ox (Zoöl.), the yak.
1 other Webster entry under this spelling
Grunt, n.
1. A deep, guttural sound, as of a hog.
2. (Zoöl.)
Any one of several species of American food fishes, of the genus Hæmulon, allied to the snappers, as, the black grunt (A. Plumieri), and the redmouth grunt (H. aurolineatus), of the Southern United States; -- also applied to allied species of the genera Pomadasys, Orthopristis, and Pristopoma. Called also pigfish, squirrel fish, and grunter; -- so called from the noise it makes when taken.
Shades of meaning
Fernald has no entry of its own for grunt; he lists it under complain.
He lists it without comment; the entries above explain its neighbors.