Time to confess: tell us about a time when you used a word whose meaning you didn’t actually know (or were very wrong about, in retrospect).
Secloistered < my invention
For an unknown reason, when speaking I have been known to say secloistered <no such word, rather than sequestered or cloistered. Yeah I think I'm Merriam-Webster inventing my own words. I know darn right well the meaning of both words, however, at times my tongue has a mind of its own, speaking for itself. Embarrassing.