野外 (yě wài) refers to natural, undeveloped areas away from human settlement — wilderness, open country. It contrasts with 郊外 (jiāo wài), which means the outskirts or suburbs just outside a city, and with 乡村/乡下 (xiāng cūn/xiāng xia), which are inhabited rural villages. 户外 (hù wài) is broader, meaning 'outdoors' in general (e.g., outdoor activities), while 野外 emphasizes wild, uncultivated land.