Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
obnuntĭātĭo (obnunc-), ōnis, f. [obnuntio], in the lang. of augurs, an announcement of an opposing, adverse, evil omen: dirarum, Cic. Div. 1, 16, 29.
In plur.: obnuntiationibus per Scaevolam interpositis, Cic. Att. 4, 16, 7: comitiorum cotidie singuli dies tolluntur obnuntiationibus, id. Q. Fr. 3, 3, 2.