Japanese for “sesame seed,” a technique that results in a dappled or speckled effect when printing. When used purposefully, this effect is often paired with other layers of varying opacities to create interesting textures. The effect can also easily be obtained unintentionally (when a flatter, more consistent color is desired), resulting in the term sometimes being used as a criticism.
An example of goma zuri being used to add texture can be seen in the example below.
(Image linked from ukiyo-e.org online Japanese print database)