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(of foods containing fat or oil) smelling or tasting unpleasant as a result of being old and stale:

〈油･脂肪を含む食品が〉いやな臭い［味］がする, くさい

e.g. rancid meat

e.g. without preservatives, fat goes rancid.

rancidity |ranˈsidətē| noun

rancidly adverb

rancidness noun

early 17th century: from Latin rancidus ‘stinking’.