Longman Dictionary of Contemporary English
Wiktionary
n. A comfortable room in a dwelling, for frequent leisure use.
WordNet
n. a recreation room in a private house
Wikipedia
A family room is an informal, all-purpose room in a house often confused with a living room. The family room is designed to be a place where family and guests gather for group recreation like talking, reading, watching TV, and other family activities. Often, the family room is located adjacent to the kitchen, and at times, flows into it with no visual breaks. A family room often has doors leading to the back yard and specific outdoor living areas such as a deck, garden, or terrace.
The term family room was introduced in the 1945 book Tomorrow's House by George Nelson and Henry Wright. Chapter 7, entitled "The Room Without a Name" spoke of the need in modern life for a new "biggest room in the house" that would serve the social and recreational needs of the entire family, allowing activities that would not be permitted in the living room.
This "big room" would have furnishings and materials that were "tough", for hard use, and it should be easy to clean. In contrast with the existing " rumpus rooms" of the time, it would occasionally serve for slightly more formal entertainment, so it should be a handsome room and should have cupboards where toys, tools, etc. could be kept out of sight. At the end of the chapter, they conclude that "we should simply call it the 'family room.'" The distinction between a family room, living room, and recreation room is fluid, but can be classified according to three characteristics: location, function and design. In homes with more than one, the family room is less formal, both in function and furnishings and is located away from the main entrance, while the living room is usually the more formal, reserved for guests, special occasions and the display of items such as antiques or artwork. It is typically located in the central part of the house towards the front. The recreation room is typically in the basement and used for games and playtime.
In homes with only one, the terms are generally used interchangeably. In floorplans, a " great room" is where the living room and family room are combined into one high-ceilinged room adjacent to the kitchen.
Usage examples of "family room".
The slumber party took place in what the Methodists called a family room, the Catholics used as an extra bedroom, and the neighborhood’.
She would not go near the house, nor let Matt later when Alex wanted him to go and see the train Dad and Rick had set up in the family room.
The television was on in the family room and the osterizer was running in the kitchen.
Perhaps worrying what impression might be given to her visitors by her casual garb and sunlit living room, Fran Feinman tipped her head towards the chaos-filled family room.
There was already a crowd in the hall without, more and more feeding into it from every family room and pressing onto the wide platform beyond, where their boats were tied.