In all the threads Ive seen, Ive only seen references to it and have only gotten a vague ides of what it means.
What Ive gotten is that it has to do with the quality of the image steadiness and focus.
is there more to it than that?

In dye-transfer printing it refers to the precision control and/or matching of the three printing matrices in relation to the receiver stock. If the registration is off on one or more of the printing matrices, the image 'color fringes' or spearates into the three dye colors on the edges of objects in the image.

-Aaron

Note that when using a continuous contact printer, optimum steadiness occurs when a short pitch (BH-1866 perforations) negative is printed onto a long pitch (KS-1870 perforations) raw stock. Printing short pitch originals to short pitch raw stock can result in slippage, causing unsteadiness and loss of sharpness. Pin-registered printers (step contact or optical) should be used for the intermediate stages, but short production schedules may not allow labs to use these slower pin-registered printers to make the intermediates.