"Ominous"

Last night in my accounting class someone said the word "ominous" when they meant "ambiguous". No big deal. I'm sure I use the wrong word frequently. I'm also pretty sure I'm the only one who noticed. And, no, I didn't bring it to anyone's attention - until now.

So I jotted down what I thought ominous means, "impending, in a bad way". And I jotted down what ambiguous means, "unclear, could go either way". Very huge differences. I confirmed my definitions in the dictionary.

ominous - menacing: threatening
ambiguous - open to more than one interpretation

I just think it's kind of funny:
"This accounting book presents the equation in a sort of ominous way."
Response? "Yes, it can be a very menacing accounting book."