nonplussed vs vacillant

nonplussed

adj
  • Unaffected, unfazed; unimpressed. 

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

vacillant

adj
  • Vacillating; wavering; fluctuating; irresolute. 

How often have the words nonplussed and vacillant occurred in a corpus of books? (source: Google Ngram Viewer )