three-way vs threeway

three-way

noun
  • Sexual activity involving three persons; a threesome; a ménage à trois. 

  • A serving of Cincinnati chili with spaghetti and cheese. 

adj
  • Relating to three different directions. 

threeway

noun
  • a sexual act involving three people. 

How often have the words three-way and threeway occurred in a corpus of books? (source: Google Ngram Viewer )