Political term, meaning a whitewash except over something ecological. A greenwash is when an environmentally destructive corporation or institution gives itself a makeover to make itself look ecologically friendly, without really changing anything. For instance, it embraces green-sounding rhetoric and imagery, produces glossy PR about its supposed environmental initiatives and makes a show of "listening" to opponents, but it doesn't actually abandon the practices which led to its being condemned as being anti-ecological in the first place.
BP's rebranding, including a new logo with a yellow sun on a green background and slogans about looking after the planet, is a classic example of greenwash.
Greenwash is Environmental bollockspeak often uttered by the UK Labour government, which is their way of justification for higher taxes when it needs extra cash for its dry coffers.
Removal of rolling 25 year road tax exemption for classic cars. Initial 'reason' in 1997/98 was financial loss to the Treasury due to the increasing number of 25+ year cars on the road. Then when more recently challenged via a Downing Street petition, Gordon Clown cited 'environmental reasons' for the withdrawal of the rolling exemption. Gordon Brown? More like Gordon Clown! This is pure Greenwash