I call it being bookish, pronounced "bawkish"

Instance of this I remember, was genre. I had seen the word, knew what it meant, 0 clue how to say it. At work one day in my teen days and someone asks "What kind of genres do you like" (in context, we were talking about video games). I clearly had a confused look on my face and the guy that asked me that switched to insulting me for not knowing a word. It took me maybe 30 seconds to figure out the word he said and the word I knew were the same thing, but apparently that was "too long".

Now pronounce “Nukular.”