noun

• (uncountable) Light that comes from the side, causing shadows that can obscure objects of view or create strong contrasts.
  "Each great party has felt itself in honor bound to justify its men and measures by elaborate argument, and so it has resulted that the light of science has been too often a crosslight, obscuring what it sought to illumine."
• (countable) A traffic light intended principally to allow pedestrian or other traffic from a lesser roadway to cross a busier roadway.
  "When the crosslight turned green, silence was much less perilous."
• (uncountable, theater) Illumination directed at the performers or subject matter from opposite sides of the set.
  "Again, the crosslight is best designed to angle slightly upstage taking care not to produce shadows on backings."
• (uncountable) Light that results from multiple sources and different directions.
  "In building a stable for horses only, where you can have light as you wish, I would say always have crosslight, so that the rays will cross as near where the horse stands as possible."

verb

• (transitive) To illuminate from the side.