Disp - Drag
- Displacement
- Displacement factor
- Distance table
- Distilled water
- Distortion angle
- Distributor
- Distributor cam
- Distributor cap (distributor head)
- Distributor gear
- Dive
- Divergent instability
- Diverter valve (diversion valve)
- Divided axle
- Divided propeller shaft
- Divided system
- Dog clutch
- Dog-cart
- Dome light
- Donkey engine
- Doodlebug
- Door key
- Door lock (door catch)
- Door pillar
- Dope
- Doped fuel
- Double acting
- Double-barrel carburetter
- Double-deck bus
- Double-ended spanner
- Double-filament light bulb
- Double-piston engine
- Double-reduction axle
- Double-venturi carburetter
- Down shifintg (down shift)
- Down-draft carburetter
- Downstream injection
- Downwash
- Drag
