An excuse to go outside and travel, combined with the fun of a hunt, and the sociability that results from meeting other Geocachers. Given a bad name by people who don't think out their placements -- a good cache should have both permission from the land owner and a reason for being there besides the cache itself.
A great game where people hide boxes (or caches) of goodies all over thw world and register the geographic coordinates on www.geocaching.com. Using a GPS unit, users are then able to go hunting for these boxes and record in the journal, take or leave items for others, and/or transfer a Travel Bug to another location.
Geocaching is the use of virtual technology to find drunken homeless men lurking in arboretums. Or random dollar store crap. If you take the manhome, you have to leave something of equal size behind.
I paid 200 bucks for this GPS and I can't go geocaching there cause the homeless man is drinking Listerine there.
A sport in which the participants
1) Loiter suspiciously in public places that lack adequate security
2) Hide an unknown package in a high-traffic area
3) Brag about it at www.geocaching.com
4) Dare others to go find and open the package.