Irregardless
People think it means: Regardless.
Actually means: Not a damned thing.
Peruse
People think it means: To skim over or browse something.
Actually means: Almost the opposite of that. Peruse means "to read with thoroughness or care." If you peruse a book, you leave no page unturned.
Ironic
People think it means: Any kind of amusing coincidence.
Actually means: An outcome that is the opposite of what you'd expect.
Pristine
People think it means: "Spotless" or "as good as new."
Actually means: "Ancient, primeval; in a state virtually unchanged from the original." It's therefore perfectly possible to have a pristine mountain of fossilized brontosaurus bones, but if you were to buff that mountain to a lustrous shine, it would no longer be pristine.
Nonplussed
People think it means: Unperturbed, not worried.
Actually means: Utterly perplexed or confused. It comes from the Latin non plus (a state in which nothing more can be done).
Bemused
People think it means: Mildly amused.
Actually means: Bewildered or confused.
Enormity
People think it means: Enormous.
Actually means: Outrageous or heinous on a grand scale. War crimes are enormities. Extra-big bouncy castles are not.
Plethora
People think it means: A lot of something.
Actually means: Too much of something, an over-abundance.
Deceptively
People think it means: Nobody is sure.
Actually means: Nobody is sure. Specifically, we're talking about when the word is used with some other adjective. Like if somebody says, "The pool is deceptively shallow," does that mean it's deeper than it appears, or not as deep?
Interesting... Most of us already knew the ins and outs of using the word "ironic" after Alanis Morissette questionable used it in her song over and over again, but a was surprised at a few of them. I myself am not particularly word-savvy when it comes to my vocab, but I always get irked when people misuse some common phrases.
The one that gets me going the most would have to be when people say, "I could care less." Please, listen to what you're saying. It's always said when people mean they don't care about something at all, which means that if you "could care less" about something, you must care about it somewhat. Try, "I COULDN'T care less about it" next time.
Another saying that gets me (and my dad) fired up is when people ask if you are "being have." That's hay-ve with a long "a" sound. You probably don't even know what that means, do you? That's because it doesn't even make sense. What the person is trying to ask is if you are "behaving," but instead they say, "Are you being have?" Maybe it's just a Western Pennsylvania thing, but I have a feeling I'll be hearing it more than once over the holidays!
Any phrases that really irk you when said incorrectly?