One of my favorite writers, Neil Gaiman, writes about the word prevaricate (it's the first item below the Batman pictures), which he once thought meant "someone not making up their minds," was then corrected to say it means "to lie," and now finds that it really can mean either:
I think it's a word with shades of meaning, and while in the US it tends to get used simply as "to lie" (as in "All politicians prevaricate"), in the UK it's more often used as a synonym for Equivocate -- i.e. to avoid giving a straight answer... even to tergiversarate. And it's the equivocation, with its implications of putting off a decision that then shades over into meanings that aren't simply "to lie".
He goes on to cite the OED in support of that.