1. working or done in secret, especially as a spy or police officer with a hidden identity

1. in a secret way, with a hidden identity

Examples

• The undercover police officer infiltrated the criminal organization.
• She worked undercover for three years to gather evidence.
• The undercover investigation revealed widespread corruption.
• He went undercover as a journalist to expose the scandal.
• The undercover agent’s identity was carefully protected.
• They conducted an undercover operation to catch the smugglers.