From Longman Dictionary of Contemporary Englishintruderin‧trud‧er /ɪnˈtruːdə $ -ər/ ●○○ noun [countable] 1 ENTERsomeone who illegally enters a building or area, usually in order to steal something The police think the intruder got in through an unlocked window.2 WANTsomeone who is in a place where they are not wanted At first I felt like an intruder in their family.
Examples from the Corpus
intruder• Along with other equipment, intruders took a computer that was used by handicapped kids. 