And to mix it up more, I've run across plenty of professors who use the word "midterm" to refer to any test that's somewhere within the term--so you might have several midterms and then a final.

To mix things up even more, at the last college I taught at, they wanted professors to give a warning through an online tracking software if their freshmen or at-risk students (like current or former academic probation) were in danger of failing and should consider withdrawing before the final withdrawal deadline. That deadline was around midterm (i.e. the middle of the term), but since professors typically wanted to get info from one more test, and needed time to grade it and submit these warnings, which themselves had to get to the students in time to be useful, you end up with professors giving tests that would be their actual midterms about two weeks before the middle of the term.