of-the-people, bottom-up, nonhierarchical

Dictionary
grass roots (also grassroots |–gras?ro–ts|)
plural noun
the most basic level of an activity or organization : the whole campaign would be conducted at the grass roots. | [as adj. ]
• ordinary people regarded as the main body of an organization’s membership : you have lost touch with the grass roots of the party.

Thesaurus
grassroots
adjective
a grassroots movement: popular, of-the-people, bottom-up, nonhierarchical, rank-and-file.