[Piwoslaw]

What exactly is a hybrid?
(1) Is it any vehicle that has more than one type of engine?
(2) Is it any vehicle that gets its power from more than one source?

Many cars sold as hybrids do have two types of engines, internal combustion and electric, but most of them (except for plug-ins) get their power only from one source anyway - gas. On the other hand, I've seen normal ICE cars branded as hybrids only b/c they are dual fuelled - CNG/LPG plus normal gas.
Vovlo, BMW, VW, etc., say the eco versions of certain models have regenerative braking, which in this case means they have a beefed up battery and the alternator switches off when accelerating and on while engine braking. Is this really regen? And is it enough to slap a 'Hybrid' sticker on?

What about the following example: Imagine a totally ecomodded ride. Everything that normally hangs on the engine is now electric - water pump, oil pump, A/C, vacuum pump (diesels), maybe even the high pressure fuel pump (commonrail) or electronically actuated valves. It has a plug-in block heater, transmission heater, fuel heater, and cabin heater. The battery is charged at home when needed, other than that by roof PV, exhaust TEG, small alternator that kicks in when engine braking. Is this car a hybrid? The lack of all accessories now allows the engine to run much more efficiently (I'm guessing they are responsible for up to 30% of the power and/or fuel consumption). With a bit of luck, the electrical side won't need charging at home, so it's just a super efficient ICE car. But if we charge do it at home, then it's a hybrid?