These aren't commonly-used words, these are very obscure words the students are being asked to define. If a bunch of students all settle on the same completely-wrong definition, it's a fair guess they were cheating.
With an astoundingly high false positive rate, assuming it's a multiple choice test.
The guys running the dictionary didn't even know what was on the test, judging by the fact that they had to guess them by looking at traffic logs. So it's highly unlikely they settled on a fake definition that just happened to match an alternative choice on a multiple choice test.