Arrogantly or presumptuously taking something for granted; showing excessive confidence without justification.
From Latin 'assumptiosus,' though this form is quite rare and literary. It combines 'assumption' with the suffix '-ious' (like 'ambitious,' 'capricious'), which creates adjectives meaning 'full of' or 'characterized by.' This is a heightened form of 'assuming.'
This word is so rare that most dictionaries don't include it, appearing mainly in Victorian literature when writers needed a fancier way to say 'arrogant.' It's linguistically interesting because '-ious' typically adds a layer of formality or old-fashionedness—'assumptious' sounds ancient and pretentious, which is almost ironic given it describes pretentiousness!
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