A runner of the more hardcore variety who enjoys running in wooded areas. A paved bike path is NOT a trail. Anything paved in any fashion is in fact, not a trail. A trail runner enjoys the elements. These include, but are not limited to, rainstorms, snow, wind, cold, heat, etc. A trail runner is generally more laid back than a road runner, and yearns to connect with nature and their bodies. Some obstacles trail runners may face are:
rocks, roots, streams, snakes, spider webs, bears, mountain lions, gigantic hills (mountains), mud, fallen trees, branches that stick out into the middle of the trail, very, very long drops that may result in death if they should happen to fall off a single track trail, dehydration, tons of blistering...
Trail runners often run much longer and farther distances than road runners do, including 50k, 50 miles, 100 miles. Many can be found in California, but are found across the US including Colorado, Virginia, West Virginia
"Why is that guy so awesome?"
"Because he is a trail runner."