IPA: /θiˈɛstɪkli/
KK: /θiˈɛstɪkli/
In a way that relates to the belief in a god or gods.
She approached the problem theistically, considering the divine influence in her decisions.
The word 'theistically' is formed from 'theo-' (from Greek 'theos', meaning god) and '-istically' (a suffix used to form adverbs from adjectives, indicating a manner or characteristic). Therefore, 'theistically' refers to a manner or characteristic related to the belief in a god or gods.
Think of 'theo-' meaning god, and remember that 'theistically' describes something done in a manner related to belief in a god.