"Borderline autism is not an official term or diagnosis. Instead, it is an informal term referring to less severe ASD symptoms.

Someone might describe themselves as having borderline autism when:

    •they suspect they have traits of ASD but do not have a diagnosis
    •they have some symptoms of ASD but do not meet the criteria for ASD
    •they have an ASD diagnosis with a severity of level 1
    •they received a diagnosis of Asperger’s disorder before 2013
    •they say they have high functioning autism
    •they mask their symptoms"
    
from MedicalNewsToday https://www.medicalnewstoday.com/articles/borderline-autism-in-adults