The definition of a goose is a type of bird, specifically, it is any bird that is a member of the family Anatidae. The word goose also typically refers to a female bird, in contrast to a gander which refers to a male bird. The word goose can even refer to a female bird that is not actually a goose, as is the case with gander.
The plural form of goose is geese (not gooses). Geese are native to North America, among other places, and many geese, such as Canadian Geese, migrate several thousand miles per year to avoid the cold northern winters.
Geese are also cultivated and harvested by farmers for food. Goose is a traditional dish for Christmas -- the so-called Christmas Goose -- and is available from many grocery stores, such as Whole Foods, during Christmas time.