illegal resident; illegal alien; visa overstayer
Refers to a person staying in a country without legal permission, including those who entered illegally or overstayed a visa. Often used in legal, immigration, and news contexts.
Illegal residents may be ordered to leave the country.
He stayed on after his visa expired and became an illegal overstayer.
不法入国者 specifically refers to someone who entered the country illegally, while 不法滞在者 includes both illegal entrants and those who entered legally but stayed illegally (e.g., visa overstayers).
非正規滞在者 is a more neutral or bureaucratic term sometimes used in official contexts, whereas 不法滞在者 carries a stronger legal connotation of illegality.
Compound of 不法 (illegal) + 滞在 (stay) + 者 (person). The term is a straightforward modern coinage reflecting legal and immigration concepts.