Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† crĭtĭcus, a, um, adj.,  =  κριτικός, fit or suitable for deciding, capable of judging. 
- I.  Adj., only as a medic. t. t. (cf. crisimus), decisive, critical: accessio morbi, Aug. Conf. 6, 1 fin.
More frequent,  
- II.  Subst.: crĭtĭ-cus, i, m., a critic, Cic. Fam. 9, 10, 1 (also ap. Suet. Gram. 14); Quint. 2, 1, 4; Hor. Ep. 2, 1, 51.