grass roots
plural noun
1- the most basic level of an activity or organization（活动或组织的）基层：
as modifier improving the game at grass-roots level.提高基层的比赛水平。
1.1
- ordinary people regarded as the main body of an organization's membership（作为组织主体部分的）基层群众：
you have lost touch with the grass roots of the party.
你疏远了党的基层群众。