Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
con-discĭpŭlus, i,m., a school-mate, companion at school, Cic. Tusc. 1, 18, 41; id. Att. 5, 19, 3; Nep. Att. 1, 3; Sen. Ep. 66; Quint. 1, 2, 26; 2, 2, 12; Suet. Ner. 22; id. Vit. 14; Plin. Ep. 1, 19, 1.