The word "Nonplussed" means being unsure about what to say, think etc
Basically, the word "Nonplussed" is used to describe when one is surprised or confused to the extent they are unsure on how to react.
Based on the use, the word is an adjective because its describes a situation(noun)
In conclusion, the word "Nonplussed" means being unsure about what to say, think etc
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