Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. percussus, a, um, Part., from percutio.
2. percussus, ūs, m. [percutio], a beating, striking (poet. and in post-Aug. prose): caducis Percussu crebro saxa cavantur aquis, Ov. P. 2, 7, 40; Sen. Q. N. 2, 6, 3: venarum, Plin. 7, 51, 52, § 171: non sentire percussum, not to feel the injury deeply, Sen. Ira, 3, 25, 3: contra scorpionis percussum, App. Herb. 31, 7.