Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mātrĭcīda (scanned matrĭcĭda, Sid. Carm. 5, 291), ae, comm. [mater-caedo], a mother’s murderer, a matricide (rare but class.): quem scribis certissimum matricidam, Cic. Q. Fr. 1, 2, 2; Nep. Alc. 6, 2: cantavit Oresten matricidam, Suet. Ner. 21.
In tmesi: matrique cida Nero, Aus. de XII. Caes. 35 (al. matrīcīda Nero).