IPA: //ʌnˈθiːəˌrɛtɪkəl//
KK: /ʌnˈθiːəˌrɛtɪkəl/
Not based on theory; practical or real rather than abstract or hypothetical.
The untheoretical approach to solving the problem proved to be more effective than the theoretical one.
Untheoretical → It is formed from "un-" (meaning not) and "theoretical" (from Greek "theoria", meaning contemplation or speculation). The word "untheoretical" means not based on theory or speculation, indicating a practical or empirical approach instead.
Think of 'not' ('un-') being applied to 'contemplation' ('theoria') — this helps you remember that 'untheoretical' refers to something that is not based on theory.