Never used independently in modern Chinese - it is the old form later written 坰 (the far countryside). The outer stroke is the 冂 'borders' radical, the same enclosure seen in 冒 and 再.
register
Archaic; you meet it only in old texts and etymology notes, replaced everywhere by 坰 or 郊外.
The 冂 radical pictures distant boundary lines enclosing open country. Here it both spells the jiōng sound and gives the meaning - the land far beyond the city.
