In psychology/psychiatry, NOS means Not Otherwise Specified (as stated above). NOS means that you may have symptoms of a certain type of disorder, but don't quite meet all the diagnostic criteria for a specific disorder. So, if you were diagnosed Anxiety Disorder NOS, you have symptoms of anxiety disorders and the symptoms are troublesome and affecting your daily functioning, however, you may not meet the diagnosis for a specific anxiety disorder (panic disorder, ocd, ptsd, generalized anxiety, etc).