Definitions:

1. a department responsible for the security of the institution's property and workers noun
   • the head of security was a former policeman
2. freedom from anxiety or fear noun
   • The watch dog gave us a feeling of security.
3. measures taken as a precaution against theft or espionage or sabotage etc. noun
   • military security has been stepped up since the recent uprising
4. property that your creditor can claim in case you default on your obligation noun
   • bankers are reluctant to lend without good security
5. the state of being free from danger or injury noun
   • we support the armed services in the name of national security

Synonyms:

• certificate
• protection
• security department
• security measure
• security measures
• security system
• surety