I think of it as a developmental disorder. My DS2 has ASD and his development is disordered. But that's not the whole story as some areas never 'catch up' and develop differently. Hie brain operates differently to a neurotypical one. He senses the world differently and in his case he's mostly under sensitive.
The NAS talks of the triad of impairments, difficulties with social communication, interaction, imagination and added to that rigidity of thinking, need for routine or obsessional interests etc. They call it a lifelong developmental disability. Though some with ASD or AS may disagree that it's a disability, more a difference.