You run your mouse over the word and a little window pops up. (highlighted word)
How do you turn that off? I am running Firefox.
You can't copy and paste or some other things I can't think of right now. It's just a random word in someones post. You folks have seen it ,,,,right?

 

If I recall the highlighted word was green. Install an ad blocker and they should disappear.

I am using AdBlock Plus.