Different definitions
of a Hybrid Vehicle

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.
Source: sol.crest.org/renewables/

A vehicle with more than one power source such as a small internal combustion engine and an electric motor.
Source: centrica.com/

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.
Source: carleton.ca/~dkarman/