CALEFACTORY is a 11 letter word that starts with C.

1. \Cal`e*fac"to*ry\, a. [L. calefactorius.]
   Making hot; producing or communicating heat.
   
   

2. \Cal`e*fac"to*ry\, n.
   1. (Eccl.) An apartment in a monastery, warmed and used as a
      sitting room.
   
   2. A hollow sphere of metal, filled with hot water, or a
      chafing dish, placed on the altar in cold weather for the
      priest to warm his hands with.