illicit (adj.)
- actionable
- adulterous
- anarchic
- anarchistic
- anomic
- banned
- barred
- black-market
- bootleg
- chargeable
- clandestine
- contraband
- criminal
- extramarital
- felonious
- flawed
- forbidden
- furtive
- illegal
- illegitimate
- impermissible
- improper
- incestuous
- irregular
- lawless
- nonlegal
- outlaw
- outlawed
- prohibited
- punishable
- secret
- sneaky
- taboo
- unauthorized
- unconstitutional
- under-the-counter
- under-the-table
- underhanded
- unlawful
- unlicensed
- unofficial
- unsanctioned
- untouchable
- unwarrantable
- unwarranted
- verboten
- wrong
- wrongful
