Geocaching is a popular outdoor activity that involves finding hidden containers, called caches, using GPS coordinates. If you're looking for synonyms for geocaching, there are a few words that fit the bill. One such term is "treasure hunting," as geocaching is often described as a modern-day treasure hunt. Another good synonym is "waymarking," which refers to the practice of locating and marking specific locations using GPS technology. "Letterboxing" is another related activity that involves finding hidden boxes that contain rubber stamps and logbooks. Lastly, "scavenger hunting" could also be used to describe geocaching, as participants need to use clues and GPS coordinates to locate hidden items.