Mostly seen in the literary phrase 一望无垠 ('a boundless expanse as far as the eye can see'), used for deserts, plains, oceans and skies, anything that seems to have no edge.
Earth radical on the left, 土. It anchors the meaning in land and ground, the edge or limit of a stretch of terrain. Same family as 地 ground, 境 border, 坡 slope.
