The term 'PARTICIPATES IN A MARATHON' can be summarized by the solution 'RUNS', which is a four letter word. Running a marathon is a long-distance running event that typically covers a distance of 26.2 miles. It is a popular event for athletes and recreational runners alike, and requires a great deal of physical and mental preparation. Participating in a marathon is an accomplishment that many people strive for, and it is a great way to challenge oneself.