Refers to a person who enters a property or area without permission, often in a legal or security context.
The trespasser was arrested by the police.
We often see trespassers on this land.
侵入者 is a more general term for 'intruder' or 'invader', while 不法侵入者 specifically emphasizes the illegality of the entry.
Compound of 不法 (illegal) + 侵入 (intrusion) + 者 (person).