Homesteading is a lifestyle of self-sufficiency. It is characterized by subsistence agriculture, home preservation of foodstuffs, and it may or may not also involve the small-scale production of textiles, clothing, and craftwork for the household use. Homesteading is not defined by where someone lives, such as the city or the country, but by the lifestyle choices they make.
A great blog by a Brooklyn Treehugger: An Experiment in Subsistence Farming, Brooklyn Style. This guy even planned for garage to barn conversion...Complete with a slaughterhouse and chicken coops! WOWZA.