Chimei (赤眉) refers, as an umbrella term, to one of the two major agrarian rebellion movements against Wang Mang's Xin Dynasty, initially active in the modern Shandong and northern Jiangsu regions, that eventually led to Wang Mang's downfall by draining his resources, allowing the leader of the other movement (the Lülin), Liu Xuan (Emperor Gengshi) to overthrow Wang and temporarily establish an incarnation of the Han Dynasty under him. Eventually, Chimei forces would overthrow Emperor Gengshi and place their own Han descendant puppet, teenage Emperor Liu Penzi, on the throne briefly, before the Chimei leaders' incompetence in ruling the territories under their control, which matched their brilliance on the battlefield, to cause the people to rebel against them, forcing them to try to withdraw home. When their path was blocked by Liu Xiu (Emperor Guangwu)'s newly established Eastern Han regime, they surrendered to him.
Read more about Chimei: Rise, Confrontation With Xin Forces Under Wang Mang and Lian Dan, Temporary Submission To Emperor Gengshi, Campaign Against Chang'an, Loss of Popular Support, Flight Back East and Collapse, Aftermath