Defrag
A verb meaning to reorganise your hard drive's data. After repeated openings and closings, the data you're using gets fragmented -- ie. it's put back in various places. With the Windows "defragment" or "defrag" tool, your computer can organise reorder the data in a neater, more efficient manner. The hard drive will then have more room in which to operate, it will find data more quickly, and generally speed its operation. (Also see Registry)