Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dĕcusso, āvi, ātum, 1, v. a. [decussis, no. I.], to divide crosswise, in the form of an X, to decussate, * Cic. Univ. 7 med.; Col. 3, 13, 12; 4, 17, 6 al.