The term "undocumented immigrant" refers to individuals who have entered a country without legal authorization, proper documentation or permission. These are people who crossed international borders either illegally or by overstaying their visas and therefore do not possess valid travel documents such as passports or entry permits. They may also lack other necessary paperwork that would legally allow them to live and work in the country they have entered. The term is often used interchangeably with "illegal immigrant" but some prefer using the more neutral phrase "undocumented immigrants" as it does not carry a negative connotation or imply any wrongdoing on their part.