A rumble seat (American English), dicky seat, dickie seat or dickey seat (British English), also called mother-in-law seat, is an upholstered exterior seat which folds into the rear deck of a two-seat pre-World War II automobile, and seats one or two passengers. When unoccupied, the space under the seat's lid could be used for storing luggage. The 1865 edition of Webster's An American Dictionary of the English Language defines a rumble as "A boot with a seat above it for servants, behind a carriage." Similar to the rumble on European phaetons was the spider, a small single seat or bench on spindly supports for seating a groom or footman. Before World War I, rumble seats did not always fold into the bodywork.
Roadster, coupe and cabriolet auto body styles were offered with either a luggage compartment or a rumble seat in the deck. Models equipped with a rumble seat were often referred to as a sport coupe or sport roadster.
Rumble seat passengers were exposed to the elements, and received little or no protection from the regular passenger compartment top. Folding tops and side curtains for rumble seats were available for some cars (including the Ford Model A) but never achieved much popularity. Among the last American-built cars with a rumble seat were the 1938 Chevrolet, the 1939 Ford and 1939 Dodge and Plymouth. The last British built car with a dickey seat was the Triumph 2000 Roadster made until 1949.
- Boot, n. ...3. A box or receptacle covered with leather at either end of a coach. (Webster, Goodrich & Porter 1865, p. 152)
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