There are many synonyms for the phrase "baker's dozen," which refers to a quantity of 13 items instead of the usual 12. One such synonym is "devil's dozen," which implies a sense of mischief or wrongdoing. Another synonym is "long dozen," which may suggest a longer or more substantial quantity. "Thirteen score" is another term that can be used to describe a group of 13 items, although it is somewhat archaic. Some more modern synonyms for "baker's dozen" include "luck's dozen" and "bonus dozen," which connote a sense of extra or added value.