Sigourney Weaver starred in zero major motion-picture films released in 2013. Her film career had been highly active in earlier years, including Alien, Aliens, Ghostbusters, Gorillas in the Mist, Avatar, and several other prominent productions, but her filmography contains no feature-film release for her in 2013.
The timing can be confusing because Weaver remained visible during that period. She appeared as Elaine Barrish in the television miniseries Political Animals, which aired in 2012, and she soon returned to feature films with Exodus: Gods and Kings in 2014. The 2013 gap therefore refers specifically to theatrical feature films, not to every screen appearance.
This question also uses “major motion picture” deliberately. A voice role, short film, television production, cameo, or project released in another format would not necessarily count. In Weaver’s case, however, the standard filmography still leads to the same result: no qualifying major motion picture was released in 2013.