heads up vs threat

heads up

adj
  • Containing only two players. 

intj
  • Used as an informal warning, caution, or call for attention; pay attention! 

threat

noun
  • A person or object that is regarded as a danger; a menace. 

  • An indication of potential or imminent danger. 

  • An expression of intent to injure or punish another. 

verb
  • To press; urge; compel. 

  • To use threats; act or speak menacingly; threaten. 

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