illegal entry; illegal immigration
Refers to entering a country without legal permission; used in legal, news, and formal contexts.
He was arrested for illegal entry.
The number of illegal immigrants is increasing.
不法入国 is the broader legal term for illegal entry, while 密入国 stresses the secretive, sneaking-in manner of the act.
不法入国 is the broad legal term for illegal entry into a country, whereas 密航 specifically implies hiding aboard a vehicle to travel there.
Compound of 不法 (illegal) + 入国 (entry into a country).