Definition of "dually"

dually¹

/ˈdjuːəli/

adverb
not comparable
1. In a dual manner; doubly

dually²

/ˈdjuːəli/

noun
plural duallies
1. (automotive) A pickup truck with four wheels on the rear axle.
  Quotations
  Whatever you do, don't buy a dually. A dually is a big, diesel truck with four wheels in the back that costs three figures to fill up.
  2011, Michael Levatino, Audrey Levatino, The Joy of Hobby Farming‎, page 34