1. To become flat or flatter; SYN. flatten out.
2. To lower the pitch of (musical notes); SYN. drop.
3. To make flat or flatter.

In digital graphic creation and manipulation programs, to combine all layers of text, images, and other graphic elements into a single layer. Elements cannot be edited after the graphic is flattened, so a graphic is not usually flattened until the final step when all adjustments have been made to the individual layers. Flattening an image significantly reduces its file size and allows it to be saved in a wider range of formats. Flattening is similar to grouping in that both actions combine a set of objects. However, flattening is a permanent action, whereas a group of objects can be ungrouped. See also layering.