IPA: //ʌnˈbɪb.lɪ.kəl//
KK: /ʌnˈbɪb.lɪ.kəl/
Not in accordance with the teachings or principles found in the Bible.
The group's beliefs were considered unbiblical by many religious leaders.
Unbiblical → It is formed from "un-" (meaning not) and "biblical" (from Latin "biblicus", meaning pertaining to the Bible). The word "unbiblical" means not in accordance with the teachings or principles of the Bible.
Think of 'not' ('un-') being applied to something 'pertaining to the Bible' ('biblical') — that's why unbiblical means not aligned with biblical teachings.