Having the consistency, appearance, or qualities of butter; containing butter or resembling butter.
From butter plus the Latin suffix -aceous (having the nature of), following the pattern of words like herbaceous and sebaceous. This botanical/chemical descriptive term emerged in the 19th century.
The suffix -aceous is used in science to describe essential qualities—'butteraceous' doesn't just mean 'buttery' but specifically means something has butter's actual chemical or physical properties, which is why you'll see it in scientific descriptions of fats and oils.
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