bobtail vs heavy goods vehicle

bobtail

noun
  • The tractor unit of a semi-truck without a trailer 

  • A short, or deliberately shortened tail. 

  • A tractor which performs without its trailer. 

  • A tractor-trailer that is relatively short in length. 

  • An animal that has a bobtail, such as certain canines or nags. 

  • An open-ended straight or four flush. 

verb
  • To drive a tractor without its trailer. 

  • To drive a truck or other vehicle without its trailer. 

heavy goods vehicle

noun
  • A lorry, truck or other large vehicle used to transport cargo with a total weight of at least 3.5 tonnes. 

How often have the words bobtail and heavy goods vehicle occurred in a corpus of books? (source: Google Ngram Viewer )