A procedure or an experiment to collect any statistical data such as rolling a dice or flipping a coin is called a trial.
Random Trial or Random Experiment
When the outcome of any experiment can not be predicted precisely then the experiment is called a random trial or random experiment. In other words, if a random experiment is repeated under identical conditions, the outcome will vary at random as it is impossible to predict about the performance of the experiment. For example, if we toss a honest coin or roll an unbiased dice, we may not get the same results as our expectations.