My definition of Autism (summarised by Steve Thomas, M.Sc.)
Autism is a lifelong developmental (often inherited) biological condition that affects communication skills, the ability to make and sustain friendships, the extent that the world is perceived through the senses and even how information is processed. In particular autism impairs the ability to understand social rules, the emotional perspectives of others (empathising) and how autistic individuals think – often a greater likelihood of taking what others say or write more literally (black and white thinking). Typically autism severity differs on a case-by-case basis (hence the name Autism Spectrum), ranging from an inability to speak (or delayed language development) with difficulties living independently, to the “less severe” Aspergers end of the scale with above average intelligence and a greater likelihood of more self-sufficiency (or somewhere in the middle).
Common Autism traits may include: difficulty understanding the perspectives of others; difficulty making friends or maintaining romantic relationships; an almost obsessive interest in one or many topics; difficulty regulating emotions; needing routine or structure to balance day-to-day demands; problems sustaining employment; difficulty maintaining eye contact; typically stronger or weaker senses (i.e. difficulty processing loud noises or not noticing cuts and burns until told).
Autism Worlds-Eye Blog 