A space which straddles a land or sea frontier—whether political, environmental, or socio-economic. See Bunnell et al. (2006) Int. J. Urb. Reg. Res. 30, 1 on transfrontier zones and resistances in Bintan, Indonesia, and Duffy (2006) Polit. Geog. 25, 1 on the politics of transfrontier conservation areas.