Trial run is a term used to describe a TEST or practice session of a process or system. It is usually done before the actual implementation of the process or system. The two crossword solutions for the term trial run are TEST (4 letters) and PREP (4 letters). TEST stands for a procedure or set of questions designed to evaluate skill, knowledge, aptitude, physical fitness, or classification in many different fields. PREP stands for preparation, which is the act of getting ready for something.