cre·na·tion \krēˈnāshən, -reˈ-, -rə̇ˈ-\noun (-s) Etymology:crenate + -ion 1. a.: one of a series of rounded projections forming an edge (as of a leaf or a coin) b.: the quality or state of being crenate 2.: shrinkage or the shrunken condition of red blood cells exposed to hypertonic solutions in which the cell margins become crenate