GBC binding:

Plastic comb binding.

GSM:

Unit of measurement used to measure paper weight (and so thickness) in printing.

Galley Proof:

A proof of text copy before it is formatted for the page.

Galleys:

The printing term for long metal trays used to hold type after it has been set but before the press run.

Gang:

Getting the most out of a printing press by using the maximum sheet size to print multiple images or jobs on the same sheet. A way to save money.

Gatefold:

A paper fold in which both sides are folded across the middle of the sheet in overlapping layers.

Gathering:

Placing the sections of a book in the correct order for binding.

Generation:

Stages of reproduction from original copy. A first generation reproduction yields the best quality.

Ghost bars:

A quality control method used to reduce ghosted image created by heat or chemical contamination.

Ghost halftone:

Halftone that has been screened to produce a very faint image.