Despite the latest publication of Diagnostic and Statistical Manual of Mental Disorders-5th edition (DSM-5), there is still no universally agreed definition on autism spectrum disorder (henceforth, autism) within the context of increasing prevalence of the condition worldwide. The aim of this paper is to bring together the operating definitions of autism from the West and the East for the possibility of establishing an inclusionary conceptual definition. To do so, two main nosological systems – DSM and International Classification of Diseases (ICD) – from the West and one – Chinese Classification of Mental Disorders (CCMD; including TCM) – from the East have been examined in this paper. Hopefully, it can provide us a better understanding of the enigmatic syndromic disorder for the purpose of preparing appropriate inclusive treatment plans for individuals with autism throughout the world – West and East as well as the rest.