The phrase "legendary screenwriter" refers to a highly respected and well-known writer who has achieved great success and made a significant impact in the field of creating scripts for movies or television. Full definition
An abundance of subplots are expertly woven together by legendary screenwriter / director Richard Brooks (Elmer Gantry) in Deadline — U.S.A.. (bloody-disgusting.com)
In Molly's Game, legendary screenwriter Aaron Sorkin (Moneyball, The Social Network, The West Wing) almost falls foul of the rule. (nme.com)
The involvement of legendary screenwriter Robert Towne, albeit in an uncredited capacity, points to another possible point of entry, but Cisco Pike has been stubbornly resistant to any such revisionist attention (vaguevisages.com)