Merrythought is a somewhat obscure word that describes the bone in a bird's wishbone. However, it does have a few synonyms that can be used interchangeably. One such synonym is "furcula," which is also used to describe the wishbone in birds. Another synonym is "clavicle," which is a more commonly used word to describe the collarbone in humans. Additionally, "wishbone" itself could be considered a synonym for merrythought. While there are not many synonyms for this word, these options can be useful for those seeking alternative ways to describe the bone in question.