one of several metal boxes placed backstage in the floor (floor pocket) or wall of a theater and containing jacks for electric cables used in lighting units.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for stage pocket
Historical Examples of stage pocket
Stage-pocket capacity for one or more arc lamps should always be provided.Motion Picture Operation, Stage Electrics and Illusions
Henry C. Horstmann