Holomonic is how the programming control type works, behind drive train where you have the capability to divorce the drive bases orientation away from its main drive direction creating a 2D drive.(Where a drive can drive a straight line and still rotate)
http://www.youtube.com/watch?v=p9WHMssEF4U what a good representation of a holomoic drive mode looks like. teams 1640 ocolate drive is anouther.
A crab drive is not a holomonic drive because it can not do the 2D drive motion.