In multi-color printing, an allowance of overlap for two colors printed adjacent to each other, as a means of compensating for misregister and to avoid gaps between colors.
In typography, an indentation cut into the intersection of strokes on a letter, particularly in early photographic typesetting and especially when setting bold typefaces. The problem of bleed arose often, due to changes in focus, light-exposure intensity, and ink bleeding during printing. Any alteration of one or more of these factors resulted in the intersections of the letters not looking sharp on the final print. As a means of compensating for this problem, traps are cut into these problem spots, so that photographic and ink bleed will bring the interesection optically out where it belongs. As can be expected, this form of type needs to be redesigned a number of times before the correct amount of compensation is achieved.
One particular problem with traps is that they become visible when setting large point sizes.