Synonyms of unofficial

2 Syllables
bootleg, backdoor
3 Syllables
personal, pirated, black-market, bootlegged, informal, outlawed, unfussy, illegal, private, throwaway, nonpublic
4 Syllables
unapproved, extralegal, unsanctioned, unconfirmed, low-pressure, free-and-easy
5 Syllables
unauthorized
6 Syllables
uncorroborated