CASUIST is a 7 letter word that starts with C.

1. \Cas"u*ist\, n. [L. casus fall, case; cf. F. casuiste.
   See {Casual}.]
   One who is skilled in, or given to, casuistry.
   
         The judment of any casuist or learned divine concerning
         the state of a man's soul, is not sufficient to give
         him confidence.                          --South.
   
   

2. \Cas"u*ist\, v. i.
   To play the casuist. --Milton.