I was visiting my brother's family recently, watching nieces and nephews chase their new kitten around. The kitten would escape pursuit by jumping up on the sill of an open window, and I warned them, "Hey, be careful kitty doesn't defenestrate herself!"
My brother, whom I consider well educated, asked me what the heck 'defenestrated' meant, so I told him to look it up. He produced a fairly thick paperback dictionary, flipped through it for a few seconds, and declared that it wasn't a real word.
I took the dictionary from him and looked, and sure enough there was no listing for 'defenestrate'. So, I threw it out the window.