The last "big car" GM made, the last ones were made in 1996. Created in the early 60's, the Cadillac Fleetwood was a monstrous car by any standard. It slowly decreased in size after the mid-70's, along with the other B-body types GM made, including the Caprice, and the Impala SS.
The car is usually adorned with the usual Cadillac luxury items, such as electronic climate control, heated rear view mirrors, all-leather interior, and so forth. It was a popular choice for limosuines, as it was big enough to begin with.
It is synonymous with the term "land yacht."