nonplussed

adjective2

1. •
   Unsure how to act or respond; bewildered, perplexed.

   • [N]ote the honest Quaker vvas nonplussed, and greatly surprized at that Question. — 1724
2. •
   (informal, nonstandard) Unaffected, unfazed; unimpressed.

   • And while many of us might be a little taken aback if Mom showed up at our offices, Secrist is utterly nonplussed, even happy about it. — 2002