Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sternūtāmentum, i, n. [sternuto], a sneezing (post-Aug.): sternutamenta erunt observanda, Sen. Ira, 2, 25, 4; Scrib. 10 (in Cic. Div. 2, 40, 84, the better reading is sternumenta).