- an especially active, vigorous advocate of a cause, especially a political cause.
- of or relating to activism or activists: an activist organization for environmental concern.
- advocating or opposing a cause or issue vigorously, especially a political cause: Activist opponents of the president picketed the White House.
“one who advocates a doctrine of direct action,” 1915; from active + -ist. Originally in reference to political forces in Sweden advocating abandonment of neutrality in World War I and active support for the Central Powers.