Characterized by or full of abuse; abusive in nature.
From abuse + -ious (suffix meaning 'full of' or 'characterized by'), an archaic adjectival formation that competed with 'abusive' but lost.
English speakers essentially had a 'word competition' between 'abusious' and 'abusive' during the development of the language—'abusive' won because it was simpler and more efficient.
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