Definition: The training phase right before a long distance event (such as a marathon) when a runner starts to cut back on his or her mileage. This reduced training phase gives runners a chance to rest, recover, and mentally prepare for their race.
Tapering doesn't happen in life. It only happens in running. Is there any other time when you ramp up your effort and energy, rack up new and exciting goals, and then just stop? I mean, yes, that's sometimes called, "Quitting". And when we were preparing for the Nashville Marathon in 2010 instead of properly tapering, we just stopped running.
But a proper taper for a 1/2 marathon means reducing your miles the week before(ish) to pre-training levels. For me, this means a week of 2-3 mile runs. That's a 30 minute run. It takes me longer to find my shoes than to actually run this distance. Runners tend to be very agitated in this phase. First of all, we have lots of time on our hands. It confuses us. Also, we have a big race coming up, and we're nervous about it. How do we deal with nerves? By running- oh, wait.... we're running less. So we get to just sit with the nerves.
This week is also when the nitty gritty of race-day logistics becomes a reality. When do I pick up my packet? How am I getting to the starting line? Is my family coming? What am I going to wear?
[Packet Pickup Definition: Before you get to the starting line you need to acquire your race number (bib), and perhaps a gear check tag (plastic number to tie to your bag if you want them to hold it for you while you run), and any other goodies people want to shower you with (anything from Chapstick samples, nail files, coupons for smoothies, etc). You'll also get your t-shirt or other race swag- which is the real reason you signed up for the race. Anyway, you have to get in a line and sign a waver and then volunteers will hand you a bag with all of this stuff in it. This is "Packet Pickup"]
I think that runners, as a group, are generally very bad at this type of logistical planning. We're much more focused on the immediate, "where are my shoes?" questions. "How much further?" "What's going on with my hamstring?" So the tapering phase is frustrating.