/ak"teuh vist/ , n.
1. an especially active, vigorous advocate of a cause, esp. a political cause.
adj.
2. of or pertaining to activism or activists: an activist organization for environmental concern.
3. advocating or opposing a cause or issue vigorously, esp. a political cause: Activist opponents of the President picketed the White House.
[ 1905-10; ACTIVE + -IST ]