snorkel vs undulate

snorkel

verb
  • To use a snorkel. 

noun
  • A snorkel parka. 

  • A retractable tube fitted in diesel-engine submarines to allow sufficient ventilation that the engines may be used at periscope depth. 

  • A hollow tube, held in the mouth, or mounted on and opening into a diving mask, used by swimmers for breathing underwater. 

undulate

verb
  • To appear wavelike. 

  • To cause to resemble a wave 

  • To cause to move in a wavelike motion. 

  • To move in wavelike motions. 

adj
  • Changing the pitch and volume of one's voice. 

  • Wavy in appearance or form. 

  • sinuous, winding up and down. 

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