Synonyms of under-the-counter

2 Syllables
banned, wrongful, taboo, lawless, bootleg
3 Syllables
improper, criminal, flagitious, black-market, forbidden, bootlegged, outlawed, illicit, illegal, nefarious, unlawful
4 Syllables
unlicensed, prohibited, iniquitous, clandestine, actionable
5 Syllables
unauthorized
6 Syllables
illegitimate