Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
plăcenta, ae, f., = πλακοῦς, a cake, Cato, R. R. 76; Hor. Ep. 1, 10, 11; id. S. 2, 8, 24; Juv. 11, 59; Mart. 5, 39, 3; 6, 75, 1; 9, 91, 18.
For an offering, Vulg. Jer. 7, 18.