Definition #1: salt-water shellfish that attach themselves to rocks, wharves, ship bottoms, and whales which is cool but probably not to whales. Definition #2: a person or thing that’s hard to get rid of.
I didn’t know about this second definition till I looked it up in the dictionary and it made me pretty happy because I was going to have trouble using barnacle in an everyday sentence. It’s not a word that comes up in general conversation except for maybe at the yacht club as in: “Skip, my good fellow, these pesky barnacles are ruining Flying Fifi.” (For you non-nautical folks that’s the name of the dude’s boat). So the rest are stuck with this: “Don’t invite Bubba to the corn feed ‘cuz he’s a barnacle.” . . . We could say that but I’m guessing we’d be uninvited to everything from then on and we’d be all sad and we’d try to get people to like us again and then we’d turn into obnoxious and clingy . . . barnacles!
Okay, better not use barnacle in an actual sentence. Wouldn’t want people to think you’re . . . pompous.