A Suntan limited to areas of the body that ate not protected from the sun by jeans, a t-shirt and shoes( i.e. the face, neck forearms, and the lower half of the upper arms, but not the chest, back, lower body or feet.
This suntan is most often seen on people that spend time in the sun, but not in a swimsuit. The iconic image that typifies a person with a farmer tan would be a person from the midwest or northern US, a farmer or gardener, an older hobbyist (rc cars or planes) a mechanic, a construction worker, etc. It is most often used as a derogatory term to describe a person that is unsophisticated, has no life, does not live near the beach and therefore unfamiliar with beach and surf culture and ettiquite (see kook) an uncouthe person and/or a geek.
(at the beach)
Person 1: "Oh my god, there are so many tourists I could barely find parking."
Person 2: "How do you know they're tourists?"
Person: "How could you not know?! Look at all the farmer tans everywhere - I'm going snow-blind from all this paleness."