nonplussed

About 0.24 uses per million words.

Meaning

1. adjective Unsure how to act or respond; bewildered, perplexed. .mw-parser-output .defdate{font-size:smaller}
2. adjective Unaffected, unfazed; unimpressed.
3. verb simple past and past participle of nonplus

Similar words

puzzled perplexed at a loss non-plussed plussed unperplexed unbemused unpuzzled nonplushed unbewildered

Often followed by

by and at when to for as the that