In a tilted, slanted, or inclined position; at an angle.
From 'a-' (on/in) + 'tilt' (from Old Norse 'tylta,' to push over or lean), forming an adverbial phrase meaning 'in a tilted state.'
Before 'atilt,' English speakers said 'aslant' and 'aslope'—these 'a-' prefix adverbs were how people described angles and positions, and they're mostly gone now, replaced by 'at an angle,' showing how language streamlines over centuries.
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