IPA: /θɪˈmætɪkli/
KK: /θiˈmætɪkli/
In a way that relates to a particular theme or subject.
The movie is thematically rich, exploring various aspects of love and loss.
The word 'thematically' is formed from 'theme' (from Greek 'thema', meaning a subject or topic) and the suffix '-ically' (meaning in a manner relating to). Thus, 'thematically' refers to something that relates to or is expressed in terms of a particular subject or theme.
Think of 'theme' as the main subject of a discussion, and remember that 'thematically' means relating to that subject in a specific way.