If a conversation with someone leaves you scratching your head and wondering what point they were trying to make, you are nonplussed: bewildered, puzzled, often speechless.
Interestingly, there is no word plussed. You can only be nonplussed. People are nonplussed when they’re astounded, exasperated, or at a loss. "I'm nonplussed," you say when your mother tells you she's marrying her 25-year-old personal trainer. "I'm nonplussed," you say when your boss fires you, even though he tells you you’re the best employee he's ever had. Since so many things are confusing and odd, there’s a lot in life that can leave you nonplussed.