This term is pretty vague. This paragraph describes it pretty well however:
Dry camping means different things to many people. The common
definition I hear from people is camping in a location where
electric/water/sewer connections are not available at each site. This
definition is very broad and includes everything from camping at a
commercial campground with centralized facilities to driving out into
the woods and pulling off into the trees.
You may have more luck looking up dispersed camping.
Dispersed camping is the term used for camping anywhere in the
National Forest OUTSIDE of a designated campground. Dispersed camping
means no services; such as trash removal, and little or no facilities;
such as tables and fire pits, are provided. Some popular dispersed
camping areas may have toilets.