adjective

illicit

ih-LIS-it/ɪˈlɪsɪt/

Not allowed by law, rules, or accepted standards.

The investigation reveals an illicit trade in stolen medical supplies.

A person secretly exchanges a hidden package while a guard blocks the area and others point out that the act is forbidden by the rules.

Etymology

The negative prefix reverses the idea of being allowed. The same verb underlies licence, so illicit expresses the absence of the permission that a licence grants.

In context

American Enterprise Institute presenter39:01

So legalization makes the illicit market a paper tiger,

Marijuana legalization, potency, and reform - Full interview with Mark Kleiman | VIEWPOINT

CUNY TV presenter16:36

illicit drug use, then it's permissible to punish

The Battle for the Constitution and Pelosi’s Originalism-Justin Driver | The Open Mind

More examples

The company conceals illicit payments to public officials.
Their illicit affair threatens both of their marriages.
The league suspends players for illicit use of performance-enhancing drugs.

Forms

illicitly adverb — In a way that is forbidden.

Similar words

illegal: Specifically violates the law, rather than rules or social standards.
forbidden: Emphasizes a ban imposed by a rule or authority.
improper: Violates accepted standards of behavior without necessarily breaking the law.