Since I'm the troublemaker who pestered Paul about this, I'll add a couple of comments to his already great start:
BERLINA:
Closed bodywork with fixed top (sometimes with a removable part), 4 seaters or more, 2 or 4 doors (but also 5 with the back door), 4-windows.
a.k.a. : Limousine (Germany)
Berline (France)
Saloon (GB)
Sedan (USA) Also 4-door hardtop (originally hardtop convertible, same as GB pillarless saloon.) 1950s/60s usage: "post." Post=pillar.
FAMILIARE - GIARDINETTA:
Closed bodywork with fixed top (sometimes with a removable part), 4 seaters or more, back seats may be folded or removed to improve luggage room, 2 or 4 doors (but also 5 with the back door), 4-windows or more.
a.k.a. : Familcar/Kombiwagen/Kombi (Germany)
Break (France)
Estate car/Estate (GB)
Station Wagon (USA)
LIMOUSINE
Closed bodywork with fixed top (sometimes with a removable part), 4 seaters or more, with the option of 2 or more additional seats (in italian 'strapuntini', something like the dickey seats) between the front and the rear seats, 4 or 6 doors, 4-windows or more. USA: seats dickey seats are sometimes called "jump seats", a reference to paratroopers' seats in aircraft.
COUPE'
Closed bodywork with fixed top (sometimes with a removable part), 2 seaters or more (with foldable front seats in case of more than 2), 2 doors, 2 or 4 windows.
USA: 1930s usage: the number of windows (not counting the windshield) described the style: 3-window (no rear quarter window) or 5-window (small quarter window) most common. Generally 2-seaters.
1940s/50s usage:
Business coupe: no rear seat (space for salesmen's products/catalogs.)
Club coupe: This definition varies with manufacturer and model. Some close-coupled coupes with a small rear seat were called club coupes (equivalent to a 2+2 arrangement), other manufacturers used the term to describe a larger rear seating area than a 2-seater coupe (equivalent to a 2-door sedan.)
Sport Coupe: 30s usage, particularly Model A Ford: 2-seater with faux cabriolet top. Other usage at the whim of the manufacturer.
CABRIOLET
Closed bodywork opened by a foldable capote which can be supported on the body or rolled up, 2 seaters or more, 2 or 4 doors, 2 or more windows. When the seaters are 2 it is often called SPIDER
a.k.a. : Kabriolett (Germany)
Cabriolet/Decapotable (France)
Drophead Coupe (GB)
Convertible Coupe (USA) (defined by roll-up windows.) 2 doors. 30s/40s usage: Convertible Sedan: 4 doors.
SPIDER
Closed bodywork opened by a capote and hardtop, the foldable capote can be supported on the body or rolled up, 2 seaters or more, 2 doors, 2 windows.
Usually a 2-seater CABRIOLET is called Spider.
a.k.a. : runabout/roadster (USA) (side curtains instead of glass windows.)
BERLINA DECAPPOTTABILE
Closed and open bodywork, fixed b-pillar, the foldable capote can be supported on the body or rolled up, 4 seaters or more, 2 or 4 doors, 2 or more windows
GB: 3-position drophead coupe.
LANDAULET
Closed and open bodywork with a fixed top over the front seats. The foldable capote over the back seats can be supported on the body or rolled up, 5 seaters or more with the option of 2 or more additional seats (in italian 'strapuntini', something like the dickey seats) between the front and the rear seats, 4 or 6 doors, 4 or more windows. This bodywork is generally used in executive cars
Some additions that might be incorporated into the main definitions
TOURER (touring car)
USA: open 4 to 7 seater, sometimes called "phaeton" . May be the same as Berlina decappotabile.
RUMBLE SEAT ROADSTER
USA: roadster with a 2nd, smaller seat located where a trunk or boot would normally be. Sometimes known as "mother-in-law" seat.
I gotta run, I'll add more when I can.
