A person who helps, encourages, or supports someone in doing something wrong or illegal.
From abet (Old French abeter) plus the agent suffix -er, which creates a noun for someone who performs an action. This is the standard formation for creating 'one who abets.'
An abetter is legally as guilty as the main wrongdoer—if you knowingly help someone commit a crime, you're not just a bystander, you're an active participant in the eyes of the law!
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