Is it considered plagiarism for a professor to use uncited sources in teaching materials? I have a professor at my university who uses content from an un-cited textbook that he has never referenced anywhere, including his green sheet (syllabus), as an additional resource. At least some slides he has used include parts of content that have been re-worded and others that are 100% the same. I noticed this by Googling for textbooks on the material we're studying in class and found that examples given in one that I found were exactly the same as what he has provided.

Would this technically be plagiarism? Should he be given the benefit of the doubt in this situation?
Plagiarism involves dishonesty: taking someone else's work and leading others to believe it is your own.

In the case of unpublished teaching materials, I don't think it's assumed that all the examples, etc., a professor uses are original unless an outside source is cited. So I wouldn't strictly consider this plagiarism (though citing outside sources is definitely preferable to not citing them).

It's possible that in your academic culture it is assumed that all of a professor's materials are original, in which case, the above would not apply.