That means she has a pervasive developmental disorder that is not otherwise specified.
I'll break that down.
PDD is an umbrella label for all autistic spectrum disorders. So if your child is being tested for PDD, someone believes your DD has behaviors/characteristics that are on the spectrum.
Austism is a PDD. It is a very clearly defined disorder, and to be autistic, you must have very specific behaviors/characteristics. My DD has some autistic behaviors, but not enough to label her as austistic.
Aspergers is a spectrum disorder and therefore a PDD. Aspergers kids also have special characteristics. My DD did not have Aspergers behaviors.
Therefore we were left with a PDD-Not Otherwise Specified (NOS) diagnosis. She is "on the spectrum" but does not have autism. She was diagnosed by a state psychologist.
My DD's weaknesses are in social interactions. She does not read social cues very well. She has trouble initiating and maintaining conversations with peers. She has trouble with eye contact. She would rather play alone. To the untrained eye, however, she looks perfectly "normal." Most of my friends were shocked at the diagnosis, but when I explained it, they said, "oh yes, I've seen that with her."
My DD is very high functioning and will attend a normal kindergarten this year.
She has an IEP (individual education plan) at her preschool and goes to a social skills class 3 days a week. She has made great progress just in the past six months since her diagnosis.
I wish you and your DD luck in your journey. Diagnosis is a long process, but it's a beneficial one because once your find the problems, you can start addressing them!