A word that is used in western civilisation
to signify someone who does not conform to societal norms
There are several different types of weirdo. Generally you can judge whether people would consider someone a weirdo by examining their opinions, lifestyle and outward appearance.
If any of these factors fall significantly outside the norms of the society which you are considering, you can confidently assume that the person is a weirdo.
I will illustrate this with an examination of three types of weirdo in mainstream Australian society.
Firstly, we have the Goth. Goths are considered weirdoes because they can typically be found dressed in black clothing. Also, they often wear leather (even in Summer), dye their hair and sport tattooes, multiple body piercings and other body customisations.
Secondly, people who spend a lot of their leisure time using a computer (for whatever purpose) are considered weirdoes in Australia. This is because the norm in Australia is to play a lot of sport and spend a lot of time in social settings such as pubs, cafes and the beach.
Another category of weirdo is anyone who is deeply involved in politics. In Australian society, it is considered normal to be apathetic towards politics in general, and at best to ignore anything political as a waste of time. However, there are groups of people involved in political campaigns or even revolutionary campaigns to overthrow the Government. These people are considered weirdoes because they think too deeply about politics.
I think it's important to recognise that when you automatically think someone is a 'weirdo', you are actually judging them based on your own (or mainstream society's) standards, and not their own.