1. kept secret by the government for reasons of national security
2. arranged in categories or groups

1. a small advertisement in a newspaper or magazine, typically organized by category
Usage: usually plural

Examples

• The classified documents were locked in a secure vault.
• Access to classified information requires special clearance.
• The library books are classified by subject matter.
• She found her apartment through the classified ads.
• He placed a classified in the local newspaper to sell his car.
• The classified section contains job listings and personal ads.
• Military personnel must handle classified materials carefully.