Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS) is one of the pervasive developmental disorders and autism spectrum disorders.
PDD-NOS is a diagnosis for people who are well-described by the "PDD" label, but can't be categorized by any other disorder. It is usually milder than autism and has similar symptoms to autism, with some symptoms present, and others absent.
References
Kennedy, Diane M. The ADHD-Autism Connection: A Step toward more accurate diagnosis and effective treatmentISBN 1-57856-498-0
Yale Developmental Disabilities Clinic
Matson JL, Wilkins J, Smith K, Ancona M (2007). "PDD-NOS symptoms in adults with intellectual disability: toward an empirically oriented diagnostic model". J Autism Dev Disord. doi:10.1007/s10803-007-0422-0. PMID 17687639.