nonplussed
definition
perplexed or confused to the point of being unsure how to react
example
She was nonplussed by the unexpected turn of events at the meeting, leaving her unsure of how to respond.
synonyms
perplexedbewilderedconfused
word origin — The word 'nonplussed' comes from the Latin phrase 'non plus', meaning 'not more'. Initially, it was used in English from the early 17th century to describe someone who is at a loss for words or unsure how to react.