I'd say what's most embarrassing is using a similar-sounding 'big word' because it reveals that you are trying to show off and that you fail at even that. Today, I heard someone say, “He supersedes me in skill level.” And caught myself writing, “I’m oscillating my time between my business and creative projects.”

I'd like to say I don't judge, but... you know. In that sense, using big words that you're not comfortable with is like gambling. If you're fortuitous and use the word unerringly, you hit the jackpot! People will be wowed by the precision of the diction you hath brought and will assume in you an intellect of untold depth.

In all other cases, you'll botch the word just slightly and expose yourself as the intellectual fraud you are. Dealer, I'd like to bet my self-worth on... loquacious.