...the term astroturfing describes formal public relations projects which deliberately seek to engineer the impression of spontaneous, grassroots behavior.
AstroTurf" refers to the bright green artificial grass used in some sports stadiums, so "astroturfing" refers to artificial grassroots efforts.
We've already seen a good example of "Astroturfing" in the hand-made signs used by Peebles' paid petition gatherers. It gives the impression of a bake sale, or one of the many fundraisers given by local schools and organizations.
Nobody expected Peebles' paid signature-collectors to display signs touting the 355 housing units his ballot measure would authorize him to build, or the traffic it would create on Highway 1. But the process of cloaking a well-funded signature-gathering effort as a "grassroots" effort is known as "astroturfing", and we've already begun to see it here.