IPA: /ˌæntiˈθiːərɪkəl/
KK: /æntiˈθiərɪkəl/
Describing something that goes against or contradicts established theories or theoretical ideas.
His antitheoretical stance made it difficult for him to engage in academic discussions.
Antitheoretical is formed from "anti-" (meaning against) and "theoretical" (from Greek "theoria", meaning contemplation or speculation). The word describes something that is against or opposed to theory or theoretical ideas.
Think of 'anti-' meaning against, and 'theoretical' relating to ideas or speculation. This helps you remember that 'antitheoretical' refers to something that opposes theoretical concepts.