This is the 9126th most frequent Japanese word.
無人
Unmanned; uninhabited.
'無人' is used here to convey that the wilderness was devoid of people.
彼は無人の荒野を冒険しました。
He adventured through an uninhabited wilderness.
Here, '無人' is used as an adjective describing the island as having no inhabitants.
この島は無人です。
This island is uninhabited.
In this sentence, '無人' describes vending machines that operate without a staff presence.