noun. an extreme observation, measurement, or rating, that being, one which substantially differs from all other individuals attained. Outliers might be the outcome of error, in which case they might skew research discoveries. Such ratings can have a high level of influence on summary statistics and approximations of parametric values and their precision.
OUTLIER: "The outlier was significant enough to weigh on the scientist's mind even though he strongly disliked the idea of starting over and repeating the study."