A star who appears in movies. Real movie stars existed mainly in the 1930s, 1940s and the Fifties. Greta Garbo, Humphrey Bogart, Marlene Dietrich and Marilyn Monroe were some. Robert DeNiro, Chow Yun Fat and Keanu Reeves are others. Acting doesn't matter as much as presence, which is why Keanu is in that list. It's possible to be a movie star as well as a superstar at the same time, but that's pretty rare.