What is the meaning of kick in the pants?

The fact that you don't know might indicate that you need a good swift one! I believe a kick in the pants is the equivalent of a "wake up call", usually a means of correction, discipline and motivation. Example: Jim forgot to pick the kids up from school again today. He sure needs a swift kick in the pants!" I picture the kick being delivered to the rear of the pants rather than the front. So, in essence, you need your a** kicked!