# undercover

/ˌəndɝˈkəvɝ/ (US) · /ˌʌndəkˈʌvɐ/ (UK)

Source: https://englishreference.com/word/undercover
Updated: 2026-06-20

## Senses

### 1. secret investigation

adjective · CEFR B2

working secretly to get information, especially for the police or government.

For teachers: involved in or involving secret investigation or spying, typically while assuming a false identity.

- The undercover officer spent months living with the gang to gather evidence.
- The agency launched an undercover operation to infiltrate the smuggling ring, placing several agents in high-risk positions for over a year.

Usage: Usually placed before the noun it describes.

### 2. a secret agent

noun · CEFR C1 · Informal

a person, like a police officer, who works in secret using a fake name.

For teachers: an operative or agent who performs duties while their true identity and motives remain concealed.

- The criminals never suspected that their new driver was actually an undercover.
- The tension in the room spiked when the boss began to suspect there was an undercover among his most trusted lieutenants.

Usage: Used as a countable noun to refer to the person rather than the action.

## Examples

- The undercover officer joined the gang to gather evidence.
- After months of undercover work, the reporter finally exposed the corruption within the local government.
- The success of the sting operation depended entirely on the undercover agent's ability to maintain a convincing persona while operating deep within the criminal organization's inner circle.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.