Definition of overlay

In general: unifying theme structure bringing together all elements of an advertising campaign. Overlays are commonly used by advertising executives to help organize an entire promotion effort and/or as a tool to facilitate long-term planning.
Broadcast: acetate sheet used in television animation when producing commercials. The sheet is used to draw motions that come after those in the original drawing.
Outdoor advertising: information sheet citing the name, address, and business hours of a retailer, affixed on the bottom of geographically dispersed outdoor advertising posters. Overlay sheets offer advertiser a flexible means of letting consumers know which retailers stock their products.
Production:

1. transparent or semitransparent covering used to protect artwork or photography, or as a means to surprint instructions, corrections, changes, copy variations, or comments on art, photography, text, or an existing design. For example, color-breaking instructions for the photoengraver are usually marked on an overlay that is pasted on an original black-and-white piece of artwork. Since these instructions are not written directly on an original, the proper specifications are communicated without touching the original design. In addition, the original copy is protected from damage or smearing. Cellulose acetate or tracing tissue are most commonly used for overlay purposes.
2. shaped piece of paper, or thin sheets of paper, put on the tympan of a press to increase or equalize the impression. An overlay increases pressure on the dark portions of the plate, creating a pressure reduction on the plate's lighter portions.
3. separate transparent or semitransparent prints that can be combined to form a finished design. An overlay is used to assess how different changes in a design's individual elements can affect its overall design.

Direct marketing: Addition of data to a customer list by matching names on the data source list to names on the customer list. See also modeled list.