Would someone like to define rushing and a rushing army??

From what I've read it seems to be- A\Charging like hell from the git go and/or- B\ A predominantly hvy cav/sword combo.

What's the cutoff for these types of units for an army to be considered non-rushing? Neither A or B seem to be too popular and even though I haven't played MP yet I can kind of see why.

How's that for a noob question?