单词warchalking
n.: 免费上网标记（在墙上标示附近可免费上网）网络: 开战标记；战争粉迹；开战粉笔标记
免费上网标记（在墙上标示附近可免费上网）:
the action of drawing a symbol on the wall of a building to show that you can get a free Internet connection near that place