6
bootleg(adjective, legal, illegal, forbidden)
6
clandestine(adjective, secret, sly, legal, forbidden)
6
contraband(adjective, legal, unlawful, forbidden, illegality)
6
furtive(adjective, hidden, legal, fraudulent, forbidden)
6
taboo(adjective, illegal)
6
unconstitutional(adjective, illegal, undueness)
5
against the law(expression, adjective, idiom, wrong, illegal)
5
immoral(adjective, wrong, wicked, legal, unfaithful)
5
unsanctioned(adjective, undueness)
4
black-market(adjective, irregular, unwarranted, criminal, legal)
4
contrary to law(expression, adjective, idiom, legal, illegal)
4
dirty(adjective, wrong, informal, wicked, senseless)
4
impermissible
4
irregular
4
punishable(adjective, illegal)
3
corrupt(adjective, wrong, wicked, criminal, illegal)
3
dishonest
3
extramarital
3
iniquitous(adjective, wrong, wicked, criminal, illegal)
3
secret
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APASmart Define. (2015). illicit thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/illicit/thesaurus/synonyms
ChicagoSmart Define. 2015. "illicit thesaurus" https://smartdefine.org/illicit/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, illicit thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/illicit/thesaurus/synonyms>.
MLASmart Define. "illicit thesaurus" 13 April 2015. Web. 21 September 2026. <https://smartdefine.org/illicit/thesaurus/synonyms>