A boar that has been caught, de-nutted, released and given time to plot revenge. These are the meanest, nastiest, dog killinest hogs that we used to catch. Especially when the people who caught/cut him last time lobbed off 1 or 2 of their ears and the dogs dont have anything to grab on to. They are good eatin though.
Hog growers castrate the male pigs very early in life, often at birth. The castrated males are barrows, and the sexually immature females are gilts. The listing for market hogs on the Chicago Board of Trade used to be for "barrows and gilts." Still is, far as I know.