Definition of “security” - Learner’s Dictionary

security

noun [ U ] us uk /sɪˈkjʊərəti/
The security guard relented and let them through.Driving along in a comfortable car can give you a false sense of security.Applicants are screened to ensure that none of them is a security risk.The issue of security came up at the meeting yesterday.They seem to have a very lax attitude towards security.
BEING SAFE

B1 the things that are done to keep someone or something safe:

airport/national security
a security alarm
SAFE SITUATION

a situation in which something is not likely to fail or be lost:

financial security
job security
CONFIDENCE

confidence about yourself and the situation that you are in:

the security of a long-term relationship
→ Opposite insecurity (insecure)
BORROWING

something valuable that you offer to give someone when you borrow money if you cannot pay the money back

→ See also social security
INFORMATION

the protection of information against being stolen or used wrongly or illegally:

IT security

(Definition of “security” from the Cambridge Learner's Dictionary © Cambridge University Press)