border light stage lighting
Technical theater term: lighting a stage using only border lights (ボーダーライト), which are horizontal rows of lights hung above the stage.
See also: ボーダーライト
In this scene, they used only border lights to silhouette the actors.
Compound of 地 (ground, base) and 明かり (light). The exact derivation is uncertain; likely a technical term coined in stage lighting contexts.