a set of four cards consisting of a three-card run plus a fourth card of the same denomination as one of the others, as 2, 3, 4, 4, worth eight points. Found on https://www.infoplease.com/dictionary/double-run
This meld format is made up of all ten cards of one suit. When using the custom rule Bigger Deck, the Sevens or Nines cannot be included in a run or double run. The double run scores 1,500 points. Found on https://www.pinochle-palace.com/pinochle-glossary/