A double date is when two couples go out together on a social event. However, there are several variations of this concept with different synonyms depending on the type of companionship involved. A few synonyms for double date could be "group date" which refers to going out with more than two couples, "couple swap" which implies a more romantic connotation, and "tag-along date" which is when an extra person is added to create a group outing. Additionally, "friendly date" or "casual date" could also be considered synonymous, particularly when the event is not intended to be romantic. Overall, these variations offer a range of ways to enjoy social activities with friends or loved ones.