A person who cultivates land, usually for growing crops. I know you're probably thinking, "Oh, we don't need these people. They don't produce computers or software. They live in small towns without access to DSL or high culture. They drive big slow tractors on the highway and slow me down when I'm driving in the country." Guess what? You need them. They produce wheat for your pizza crust and tomatoes for your pizza sauce. They grow cotton for that holey underwear you're wearing. They grow sorghum, which is fed to the cattle that will eventually become your cheeseburger. You need them pretty damn desperately, so please refrain from leaning on your horn when you blast past their tractors on the highway.

Technically, a farmer can also raise livestock, but if you call a man who raises a herd of cattle a farmer... well, both the rancher and the farmer will get insulted. You shouldn't insult folks who work in agriculture. The ranchers have cows they can stampede, and the farmers have pitchforks. Both often own shotguns.