In a manner that opposes or rejects social norms; in a way that avoids social interaction or harms society.
From 'antisocial' (opposing social connection) plus the adverbial suffix '-ly.' The base 'social' comes from Latin 'socialis' meaning relating to companionship or allies.
Interestingly, 'antisocially' can mean both 'in a withdrawn way' (avoiding people) and 'in a harmful way' (hurting people)—English uses one word for two opposite causes, which creates interesting legal and medical ambiguities.
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