out·li·er 
(outlī′ər)
(outlī′ər)n.
1. One that lives or is located outside or at the edge of a given area: outliers of the forest standing in the field.
2. One that exists outside or at an extreme of a category, pattern, or expectation; an extreme case or exception: "those egg-laying outliers of mammaldom, the duck-billed platypus and the anteating echidna" (Natalie Angier).
3. A value far from most others in a set of data: "Outliers make statistical analyses difficult" (Harvey Motulsky).
4. A portion of stratified rock separated from a main formation by erosion.