What do you call a group of professors?

There isn't one single, universally accepted collective noun for a group of professors. You could use general terms like:

* Faculty: This is the most common and appropriate term.

* Department: If they all belong to the same academic department.

* Group: A simple and neutral term.

* Panel: If they are assembled for a specific purpose, such as a discussion or review.

* Assembly: A more formal term for a gathering.

There isn't a whimsical or unique collective noun like there is for some animals (e.g., a murder of crows).