The definition of a metastat is a type of statistic that is used to measure the spread of a given set of data. It is a way of summarizing the data in a concise and meaningful way. Metastats are used to measure the variability of a data set, as well as to identify any outliers or patterns that may exist. Common metastats include the mean, median, mode, standard deviation, and range. These metrics can be used to compare different sets of data and to identify any correlations or trends. Metastats are also used to determine the reliability of a given set of data, as well as to identify any potential errors or inconsistencies. Metastats are an invaluable tool for data analysis and can provide valuable insights into the underlying structure of a given data set.