As with any popular technology a Hybrid Vehicle can be defined in several ways. It all depends on a persons viepoint and context. Here are several definitions from various sources:
Broadly, any vehicle with two propulsion systems.
In electric vehicles, either (1) operates solely on electricity, but contains an internal combustion motor that generates additional electricity (series hybrid);
or (2) contains an electric system and an internal combustion system and is capable of operating on either system (parallel hybrid).
Also used to describe FUEL CELL vehicles with electric drive components.
A vehicle with more than one power source such as a small internal combustion engine and an electric motor.
A vehicle that is propelled by two or more sources of power, usually a battery and an internal combustion engine (ICE). The ICE can charge the battery, drive the wheels, or both.