sightline definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of the straight lines of unimpeded vision from various points in a theater to the stage
sightline definition by American Heritage Dictionary
also sight linenoun
A line of sight, especially one between a spectator and the spectacle in a theater or stadium.