IPA: /nɒnprəˈfɛʃərɪəl/
KK: /nɑnprəˈfɛʃərɪəl/
Not related to or characteristic of a professor or teaching profession.
The seminar was led by a nonprofessorial expert in the field.
Nonprofessorial → It is formed from "non-" (meaning not) and "professorial" (from Latin "professorius", meaning relating to a professor). The word describes something that is not related to or characteristic of a professor.
Think of 'non-' meaning not, and 'professorial' relating to a professor — so nonprofessorial means not like a professor.