Refers to a person who enters a country without legal permission. Often used in news and legal contexts.
Illegal immigrants were arrested at the border.
Synonymous; 不法入国者 is also common and may be used interchangeably.
The act of illegal entry; 密入国者 is the person who commits it.
Compound of 密 (secret, illegal), 入国 (entry into a country), and 者 (person).