intruder
gb/ɪntɹˈudɚ/ us/ɪntɹˈudɚ/
B2
English
Senses
0 senses
Noun
B2
role
1
person entering without permission
a person who goes into a place without permission
Usage pattern:
[an intruder] enters [a place]/is on [property]
Common mistake:
Don’t confuse intruder (enters a place) with interviewer (asks questions) or introducer (presents people).
Synonyms
trespasser (emphasizes being on land/property illegally.)
|
burglar (specifically someone who breaks in to steal.)
|
invader (often suggests forceful entry or a hostile presence.)
Antonyms
guest (a person welcomed or invited into a place.)
|
resident (a person who legally lives in the place.)
Collocations
an intruder entered the house
|an intruder broke in
|catch an intruder
|detain an intruder
|report an intruder
|a masked intruder
|an armed intruder
|an intruder on the property
|a suspected intruder
|fleeing intruder
Themes
crime
|security
|home
|law
Examples
- She heard footsteps downstairs and called the police to report an intruder.
- The dog barked loudly when an intruder climbed over the fence.
- Security cameras helped officers identify the intruder who entered through a back window.
Learner examples
- An intruder came into the house at night.
- The alarm went off because of an intruder.
Noun
C1
role
2
unwelcome person in a situation
a person who is not wanted in a private situation
Usage pattern:
feel like [an intruder] (in/on) [a situation/place]
Common mistake:
This sense is about social situations; for physical illegal entry, use the main security/crime sense.
Synonyms
interloper (more formal; stresses being where one doesn’t belong.)
|
outsider (emphasizes not being part of a group, not necessarily interrupting.)
Antonyms
insider (a person who belongs to the group or situation.)
|
participant (a person who is legitimately involved.)
Collocations
feel like an intruder
|an intruder in their conversation
|an intruder in the family
|an intruder in their privacy
|an intruder at the meeting
|unwanted intruder
|social intruder
|a sense of being an intruder
Themes
relationships
|social_life
|emotions
Examples
- I felt like an intruder when I walked into their private argument.
- He tried not to act like an intruder, but the group clearly knew each other well.
- She apologized for being an intruder and stepped out to give them space.
Learner examples
- I felt like an intruder at the party.
Noun
technical
C1
role
3
unauthorized computer user
a person who enters a computer system illegally
Usage pattern:
detect/identify/stop [an intruder] in [a system/network/account]
Common mistake:
In everyday speech, hacker is more common; intruder is often used in security or IT contexts.
Synonyms
hacker (broader and more common; can be neutral in some contexts, unlike intruder.)
|
attacker (emphasizes malicious intent rather than just unauthorized access.)
Antonyms
authorized user (a person allowed to access the system.)
|
administrator (a legitimate user with control privileges.)
Collocations
a system intruder
|network intruder
|an intruder gained access
|detect an intruder
|block an intruder
|track an intruder
|an intruder attempted to log in
|an intruder compromised the server
Themes
technology
|cybersecurity
|crime
Examples
- The IT team detected an intruder on the network and shut down remote access.
- Logs showed that an intruder had tried thousands of passwords in a few minutes.
- The company updated its security rules to keep intruders out of employee accounts.
Learner examples
- An intruder got into their online account.
Grammar
Dictionary form
intruder
IPA
GB/ɪntɹˈudɚ/
US/ɪntɹˈudɚ/
Syllables & stress
in - truder (2 syllables)
Stress on 2nd syllable (truder)
Word forms
Noun
- Base: intruder
- Plural: intruders
Word family
Expressions
intruder alarm
1/ɪntɹˈudɚ əlˈɑɹm/
fixed phrase
alarm that detects break-ins
an alarm that warns you about a break-in
Examples
- We set the intruder alarm before going to bed.
- The intruder alarm went off when the back door opened.
- They installed an intruder alarm after a burglary on their street.
intruder alert
1/ɪntɹˈudɚ əlˈɚt/
fixed phrase
warning that an intruder is present
a warning that someone has entered without permission
Examples
- My phone sent an intruder alert when the camera detected movement in the garage.
- The guard responded immediately to an intruder alert on the control panel.
- Staff were told to stay inside after an intruder alert.
intruder detection system
1/ɪntɹˈudɚ dɪtˈɛkʃən sˈɪstəm/
fixed phrase
technical
system for detecting unauthorized entry
a system that finds unauthorized entry
Examples
- The warehouse uses an intruder detection system with motion sensors and cameras.
- Engineers tested the intruder detection system by opening a side door after hours.
- The report recommended upgrading the intruder detection system to reduce false alarms.