/ əʊt; NAmE oʊt/ adjective
[ only before noun ] made from or containing oats :
oat cakes
oat bran
—see also oatmeal
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WORD ORIGIN
Old English āte , plural ātan , of unknown origin. Unlike other names of cereals (such as wheat , barley , etc.), oat is not a mass noun and may originally have denoted the individual grain, which may imply that oats were eaten in grains and not as meal.