Shifting Definition?

I got into a semantic discussion with a coworker last night about a word. I've had this exact discussion once before and I understand where they're coming from because in essence, they're right. However, my assertion is that the word's definition has shifted. I come here to offer my point of view and to allow you all to dictate my beliefs. The word in question is euphemism.

The discussion started with me stating that "gash" is a euphemism for "vagina" (as with all semantic arguments, they must feature the basest level of subject matter possible). I was called out for misusing the word in question because at the very least, "gash" is a neutral, if not negative way of regering to a vagina (I acknowledge that our examples may not be the best to use since many people are bashful about saying "vagina" and may actually consider "gash" to be a nicer way of putting it. My personal feelings about the word "gash" lead me to think that's not the case, but it illustrates that some words carry different baggage for different people and therefore inoffensiveness is relative).

My argument is as follows: I would wager that at least 90% of people don't know what the antonym of "euphemism" is and thus have no ability to refer to it when necessary. I certainly didn't, hence why I used "euphemism" in the first place. The antonym/s is/are mentioned in the link above, but if you didn't click it or read that far, take some time to think of what you would an offensive way to phrase an expression (a pretty poor definition, mind you). An example given for this type of thing is "snail mail" instead of postal mail. I wouldn't know what to call that if not a euphemism.

So since the antonym/s (there are three words listed as possibilites, though one specifically makes sense to me as the best antonym) are out of favor in common language, it is my belief that the original definition of euphemism has shifted (or is shifting) to cover the inoffensive, offensive, and neutral categories of substitution. Words are changing and adapting definitions all the time, so I don't see why that can't be the case here, but I could be alone. If that's the case, I will accept defeat with dignity and grace.


Incidentally, the antonym is dysphemism.