Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
tussis, is, f., a cough, Cels. 4, 4, 4; 4, 4, 6; 4, 8, 9; Col. 6, 10, 1 sq.; Plin. 23, 4, 51, § 136; 21, 20, 83, § 140; 26, 6, 16, § 30; Ter. Heaut. 2, 3, 132; Cat. 44, 7; Verg. G. 3, 497; Hor. S. 1, 9, 32: sicca, a dry cough, Cels. 4, 6: tussi liberari, Plin. 32, 8, 29, § 92.
Plur., a severe cough, Plin. 20, 13, 51, § 136.