Meaning
किंकर्तव्यविमूढ करना, उलझा देना, Surprise and confuse (someone) so much that they are unsure how to react.
Key
non (ना) plus
Link
addition के question में plus का sign ना देखकर मैं तो surprise और confuse हो गया था.
Synonyms
puzzle, pose, stop, beat, confound
Usage
Diane was nonplussed by such an odd question