dead on vs uncertain

dead on

adv

  • exactly at 

adj

  • very accurate 

uncertain

adj

  • Not certain; unsure. 

  • Not yet determined; undecided. 

  • Variable and subject to change. 

  • Fitful or unsteady. 

  • Unpredictable or capricious. 

  • Not known for certain; questionable. 

noun

  • Something uncertain. 

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