The Collaborative International Dictionary of English v.0.48:

Showbread \Show"bread`\, n. (Jewish Antiq.)
   Bread of exhibition; loaves to set before God; -- the term
   used in translating the various phrases used in the Hebrew
   and Greek to designate the loaves of bread which the priest
   of the week placed before the Lord on the golden table in the
   sanctuary. They were made of fine flour unleavened, and were
   changed every Sabbath. The loaves, twelve in number,
   represented the twelve tribes of Israel. They were to be
   eaten by the priests only, and in the Holy Place. [Written
   also shewbread.] --Mark ii. 26.
   [1913 Webster]