'Grunt' definitions:

Definition of 'grunt'

noun

The short low gruff noise of the kind made by hogs [syn: grunt, oink]

noun

An unskilled or low-ranking soldier or other worker; "infantrymen in Vietnam were called grunts"; "he went from grunt to chairman in six years"

noun

Medium-sized tropical marine food fishes that utter grunting sounds when caught

verb

Issue a grunting, low, animal-like noise; "He grunted his reluctant approval"

From: GCIDE

Grunt \Grunt\ (gr[u^]nt), v. t. [imp. & p. p. Grunted; p. pr. & vb. n. Grunting.] [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. [1913 Webster]
Who would fardels bear, To grunt and sweat under a weary life. --Shak. [1913 Webster]
Grunting ox (Zool.), the yak. [1913 Webster]

From: GCIDE

Grunt \Grunt\ (gr[u^]nt), n.
1. A deep, guttural sound, as of a hog. [1913 Webster]
2. (Zool.) Any one of several species of American food fishes, of the genus Haemulon, allied to the snappers, as, the black grunt (Haemulon Plumieri), and the redmouth grunt (Haemulon 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. [1913 Webster]
3. A U. S. infantryman; -- used especially of those fighting in the war in Vietnam. [slang] [PJC]

From: GCIDE

Redmouth \Red"mouth`\ (-mouth`), n. (Zool.) Any one of several species of marine food fishes of the genus Diabasis, or Haemulon, of the Southern United States, having the inside of the mouth bright red. Called also flannelmouth, and grunt. [1913 Webster]